The first part of this is almost always discussing archetypes, the second part is first pick orders. There's a lot more coming about what makes a good pick order and how to do that part properly, but you start with the context first so people can talk about cards that massively over or underperform before you consider where to take them first pick.
So, here's all of that info from Ravnica Allegiance. The opinions here are definitely biased towards my thoughts, but I've integrated everything I picked up from these pre-MC group discussions. I've included some real rough pick orders, but don't put too much stock in them. There are likely things I set in place early and didn't adjust enough, and by the time you have context to be in an archetype you likely have context to know which of the cards you need most as you move further down the list.
Also, for those of you drafting against the Magic Arena Bots a lot of the pick order advice can just get thrown out the window. This is how to draft against a bunch of dynamic humans often with unpredictable preferences, not a bunch of static AIs. Learn from the archetype descriptions, think about how those might perform differently against the skewed metagame and card evaluations, and adjust accordingly.
Big Picture
Because the better cards are less linear, that means that often adjacent guilds are competing for similar cards down the entire pick order. Both Orzhov and Azorius want to play Syndicate Messenger, where last set Rubblebelt Boar was almost exclusively Boros filler. This creates an effect where it's often right to be in an open guild, but you have to adjust your plan based on which colors your neighbors are competing with you for. An Azorius deck being passed to by an Orzhov player is going to have to have a different plan than one passed to by a Simic player. Your color splits rarely deviate that much, but your filler playable quality in each color does and that defines the differences.
These half contested scenarios are not the same as fighting over your guild with someone passing to you. That is still really bad and not usually fixable.
Gruul
Gruul is a good place to start, because it probably the most hampered when the wrong color of the pair is open. “Green Gruul” is good, but “Red Gruul” really struggles to succeed.
The issue with “Red Gruul” is that while the red aggressive cards are good, they count on the other color to push them through. The lower tier green cards can't do that, beyond maybe Gift of Strength. This format is also removal heavy, and if you are too trick heavy your deck can fold when it draws two threats that die to Summary Judgment or Slimebind. In addition to high quality multicolored cards, “Red Gruul” needs high power red spells like Light up the Stage to stand a chance.
“Green Gruul” has more access to beaters that don't need help to push through, like Rampaging Rendhorn. You get to save pump spells for high leverage spots and ignore more random creatures.
Gruul also has multiple two drops that pump up between Sauroform Hybrid and Gravel-Hide Goblin, but none of the three drops do this. As a result, your Gruul decks are often defined by getting high quality two drops, high quality bulky fours and fives, and throwing in whatever three drops you get. Even the multicolor Rubblebelt Runner is mediocre as it doesn't scale up, and Gruul Locket might be among the better three drops. “Green Gruul” wins again here as Steeple Creeper trades up and has real text.
I often find myself splashing in Gruul for interaction like Get the Point, or Applied Biomancy and Steeple Creeper's activation. You usually have enough mana sinks and big spells an Open the Gates as an 18th land is welcome. One warning on this splash business it to never let yourself get tricked into being base Golgari splashing red unless your deck is all multicolored cards or Gates. Sauroform Hybrid and Ill-gotten Inheritance aren’t playing the same game.
Gruul's weaknesses even when good are having issues coming back from pressure and dealing with good blockers. For the first I value having Scorchmark and sideboard blockers like Footlight Fiend that let me keep parity early or cast multiple relevant spells in a turn. For the blockers issue, adjust your tricks accordingly. Bring in Gift of Strength versus green and large Scuttlegators, Storm Strike versus black and deathtouch. I also don't mind Act of Treason because your creatures hit so hard if you clear a good blocker.
Rakdos
There are two distinct Rakdos decks in Ravnica Allegiance draft, again largely defined by base color but a bit less than Gruul.
“Red Rakdos” is just an aggro deck. You aren’t a spectacle deck, don’t think Spear Spewer is good. You just attack with good creatures and removal, have some ways to deal direct damage, and call it a day. Play Rubblebelt Recluse because it hits like a truck, and Act of Treason without sacrifice synergies is still a fine way to answer larger blockers.
The reason this deck succeeds where Gruul doesn’t is good support. Rakdos Trumpeter is worth a lot of damage in a good curve, randomly picking up a good removal spell or two goes a long way, and low power black cards like Bladebrand or Undercity’s Embrace cover the good blocker issue really well.
“Black Rakdos” can also play the aggro role, but via Dead Revels can start getting really grindy. The aggressive Rakdos cards keeping spectacle enabled really lets you get card advantage at low mana cost. The key is having card advantage creatures to doubly leverage the double rebuy. Blade Juggler is obvious, Rakdos Firewheeler is unbeatable in this way, but I’ve also liked Orzhov Racketeers and Debtor’s Transport leaving behind Spirit tokens here. Most of the same cards good in “Red Rakdos” are still good here, but you just have a deeper gameplan.
Rakdos rarely ends up splashing. Probably because Gruul sucks to splash and the Orzhov gold cards are so high priority it’s tough to reliably get them and the fixing to do it.
I have not pulled off the Goblin Gathering or Cavaclade of Calamity decks. No one I talked to had either. That alone might just be the lesson there.
Orzhov
All of the guilds are very solid in Ravnica Allegiance, but Orzhov is the easy “best” guild. Emphasis on the easy, because the baseline cards available to it are all obviously great. There's a bunch of removal and all three Orzhov multicolor commons are first pick considerable.
The biggest issue with Orzhov is how you plan on actually winning the game. The creatures are all fairly anemic, and your decks of all good removal and filler bodies really suffer as a result. Even if you kill all of their creatures they have time to draw out if it and some decks don't even care about creatures. You also have little direct or virtual card advantage if Afterlife tokens aren't relevant in a matchup, which means mana flood, blanked conditional removal, or just brute force card draw can all be issues. As much as a card like Imperious Orator looks ahead of the curve, at the end of the day it’s still a Grizzly Bear and not a relevant threat.
Solution one is having multiple Grasping Thrulls or rares. A blue splash for Chillbringer or Azorius Skyguard can also fill in, or just the hybrid Senate Griffin killing significantly faster than the two power Syndicate Messenger or Carrion Imp.
Solution two is “Black Orzhov”, where Azorius and white are contested but you get black cards like Blade Jugglers and Ill-Gotten Inheritance. You get to aggressively use removal, then have all sorts of ways to close out after getting your chip shots in. A warning: even if Blade Juggler is great you really don’t want to be paying full retail for it and having the card overlap with Grasping Thrull on your curve. If you have multiple Blade Jugglers make sure you have Twilight Panthers or two drops that attack. Even Rakdos Trumpeter is fine in a pinch if you are heavy spectacle or heavy on black ways to drain their last life.
There’s a flip side of this with much worse white aggro creatures like Prowling Caracal backed by Civic Stalwart. It isn’t good without a ton of Orzhov gold cards, but if I’m not baseline aggressive I like picking up these marginal three power attackers as a sideboard plan versus more controlling decks.
Solution three is finding some durdly enchantment or similar effect and running with it. Orzhov decks heavy on white often have this issue because the white commons don’t have any of the additive value Blade Juggler and Dead Revels provide or even just a high end beater like Debtor’s Transport. Angelic Exaltation is a really good example of the effect you want, Ill-Gotten Inheritance another that blurs the lines between the aggro and durdle. Even Screaming Shield can do the trick, just something that says if you have a couple of stupid creatures to their maybe one doofus, you will win the game.
Azorius
The blue guilds function slightly differently than the others because blue is so absurdly deep in Ravnica Allegiance. Shimmer of Possibility, Thought Collapse, Prying Eyes, Quench, and Sage’s Row Savant are all perfectly fine cards that wheel regularly. Chillbringer, Skitter Eel, and Slimebind are the best blue commons but are reasonably replaceable too, so fighting over blue doesn’t drastically change your deck.
In Azorius this depth translates to your deck just having tons of good options across the mana curve. You need two drops to function and the five drops are all really strong finishers, but if you are missing three or four drops don’t worry a ton. Stuff will come, or it won’t the low drop replacements are fine. Even playing an extra Quench is fine because it trades up for their three or four drop on the turns curving out matters.
When in doubt Azorius just has a ton of fliers capable of closing games. All of those creatures I mentioned splashing in Orzhov are just on color here.
The one avenue a “blue Azorius” deck opens significantly is low creature count Clear the Mind nonsense. These decks really need a high density of the low cost interactive blue commons to function, and if blue is contested you usually end up with a copy of everything but no shots at multiples. This is also the primary home for Dovin’s Acuity, especially if you branch to Bant and go down the Growth Spiral road as that trio is tied together by blue, so expect that powerful enchantment to underperform a bit if you are fighting Simic drafters.
Angelic Exaltation and Screaming Shield are the nonsense cards that are better in “white Azorius”. Screaming Shield has now been mentioned twice, and it wasn’t a card on my radar until having discussions right before the Mythic Championship. I drafted a fairly average Azorius deck on Day 2, slapped a Screaming Shield on some doofuses, and it was an acceptable clock. I wouldn’t advise picking it up highly, but if you get once incidentally and need a way to win it does the trick. Big thanks to Pro Tour Guilds of Ravnica Champion Andrew Elenbogen and Grand Prix Oakland finalist Hunter Cochran for pointing out this card can do work.
High Alert just kinda works regardless of your deck base color as long as you get the right filler. Sometimes you just took the slightly more powerful Senate Griffin, Chillbringer, and countermagic and not Senate Courier, Azorius Knight-Arbiter, and Concordia Pegasus before you saw High Alert. At most High Alert lightly correlates to blue filler as Sage’s Row Savant and Shimmer of Possibility help find it in dedicated decks, but generally the high toughness creatures are evasive and fine at chipping games away in normal mode. You aren’t just a defender theme deck with this card. High Alert overperforms in Azorius mirrors, shutting off Slimebind, Sky Tether, and Faerie Duelist, so even if it isn’t the best engine for your maindeck cards keep it in mind as a sideboard option.
The white tempo-aggro deck tends to perform better here, largely because Chillbringer is messed up. My one 3-0, 6-0 of the format was a triple Chillbringer aggro Azorius deck where I always won the game before the creature untapped, making Chillbringer a common flying Ravenous Chupacabra. Multiple Arrester’s Admonition and Chillbringers is a legit reason to try and beat people down, just don’t think Haazda Officer is going to do work without those tempo cards.
Simic
The different Simic decks are split by how much you want to play Applied Biomancy.
“Green Simic” wants all the Applied Biomancy it can get. The green early drops are creatures that can attack, including nonsense like Territorial Boar curving into Steeple Creeper. “Gold Simic” when the guild is comically open often falls into a similar tempo plan because all the multi-colored Simic cards are good rate creatures with adapt like Aeromunculus.
“Blue Simic” is a weird ramp-control deck. Eighteen lands, more of a mana line than a curve, hopefully multiple Slimebinds or Quenches so your two drops drawn on turn five can trade up, and probably a seven drop or two. Applied Biomancy is fine here, but since it is card disadvantage you often struggle to find a good use for multiples. You are leaning heavily on counter magic as answers, so if your opponent has Rhythm of the Wild you are basically dead.
This deck is one that doesn’t need to splash but easily can if everything falls into place, and often my true five color nonsense decks start off with a “Blue Simic” core.
Gates
The first is just getting a couple payoffs early and just moving in. The problem with this is that sometimes your filler and your Gates line up awkwardly. In my second Mythic Championship draft my first two picks were Gates Ablaze and Archway Angel, but all the good cards I saw were Azorius and all the Guildgates were Gruul. If I stuck to Gates my deck would have all green-red lands, and the only green spells would be Open the Gates. This just doesn't work.
On the flip side, you really need the Gate payoffs early to commit to this when things do line up. If I got a bunch of good Gruul playables and Gruul Guildgates with maybe a late Rakdos Guildgate, I'm just going to be Gruul splashing black and not actually Gates. Don't dive into Gates without payoffs when there's just a normal deck open instead.
Another way into Gates is just picking a few powerful cards early, then snapping up Gates out of dry packs, then realizing you have four multicolored cards with a mix of four Gates and just running with it. This is my favorite, largely because it leads to stupid stuff like Dovin, Grand Arbiter into Judith, Scourge Diva. Gateway Plaza is astounding here, and you often want exactly two along with another seven or eight Gates spread across colors. At that point you can do whatever you want.
The last way and the easiest "Gates deck" is just the half-Gates deck. You start in some color pair, often Simic, pick up a Gateway Plaza to hedge on splashes, get a couple good multicolor cards in adjacent guilds, and wind up double splashing with seven or so Guildgates. Your Gates payoff cards are solid but not insane here. This being a common end game is why I have Archway Angel as such a high pick. The card is still amazing with four or five Gates, where the other Gates payoffs lose a lot of value. As you can see in my pick orders, I'm just actively ranking the splash cards in anticipation of ending up in these decks fairly often.
My most common "half Gates" decks are Jund splash white for Archway Angel, or either blue guild double splashing. This makes sense as I'm less interested in getting super splashy when in Rakdos, so I take less of the speculative splash picks. Orzhov may want to splash, but many of the best speculative Rakdos-Azorius splashes there are removal for your already removal flooded archetype.
By the way, if your highest ranked Gate in a three color deck isn't Gateway Plaza you are doing it wrong. If you are double splash Simic it fixes for Lawmage's Binding, Gates Ablaze, and Frilled Mystic. If you take it before you have a splash card, it always lines up with whatever splashable thing you open.
Archetype Rankings
1. The open archetype. All the major archetypes are amazing when you get the cards for them. These rankings below are for when they are contested, which sometimes just happens.
2. Azorius. Blue is so deep on playables and Azorius so deep on good win conditions that this deck just tends to come together in reasonable ways regardless.
3. Half-gates, because you can just admit you chose the wrong base colors half a pack later and switch on over.
4. Orzhov, because in general the Orzhov per-card power level puts you over the top of other people's mediocre contested decks.
5. Simic, because blue playables still do work.
6. Rakdos, issues with aggressive decks against some of the format's best cards get magnified if you don't get some higher power pickups a bit late.7. Gruul
8. Full gates, because without payoffs or enough Gates you should have drafted anything else.
