How to approach deckbuilding in pool 1
So, you're new to the game and trying to figure out the best deck you can make!
Let me start by saying you should really not go looking at full deck builds. The #1 tip I can give anyone is to not go look for "best pool 1 deck!" guides. You are not likely to be able to fully complete most of them, then you have to look around for replacements and/or be sad that you can't make any top tier decks.
Instead, you should be looking at just jamming the best cards (or small packages) into your deck. Past that, it is worth considering where they come from. Specifically, everyone has access to Starter Cards and Recruit Season cards relatively early.
S-tier cards
So, these S-tier cards are the best cards. Starting this small list, we will hit on the previously mentioned "guaranteed" cards. I am not ranking these in a specific order, but just touching on the best cards and why.
Blue Marvel
Blue Marvel buffs your whole board for a very reasonable rate while having multiple potential synergies. He lines up well with other strong things to be doing in pool 1.
Iron Man
Multiplicative scaling. Iron Man almost always wins the lane he is played into.
Ant-Man
[1/4] is a great rate and not hard to activate. He also lines up well with other strong strategies as mentioned with Blue Marvel. Cheaper cards make Blue Marvel better, and Ant-Man specifically wants a lane filled, implying other cheap cards.
Sentinel
Another card that supports playing a lot of cards. Helps fill Ant-Man's lane. Helps us make use of all of our mana. Benefits heavily from Blue Marvel.
That is the end of the "guaranteed" cards, but we still have 3 more S-tier cards remaining, soooo...
Angela
Angela should be in every early pool deck you make basically. She is almost always a [2/9], again wants a full lane, and is insanely strong. I would not be surprised if she is nerfed. One of the best cards in the game, even when you have a full collection.
Ka-zar
Kazar defines one of the better archetypes. The other 1-drops than Ant-Man are not necessarily insane, but again, they help fill lanes for Angela and Ant-Man and benefit from Blue Marvel. Unlike some of the other S-tier cards, he does not auto fit in almost every deck, but rather defines a full deck.
Scarlet Witch
Some people will consider this controversial - feel free to not run her. She has a high skill cap, allowing you to break parity. Her strength is in location removal, not generation. And even if a location seems good to you, it may be better for your opponent, based on your hand and deck. If you do not want to think about this, perhaps skip over her. But she is insane for people that want to put more thought into the game.
A-tier cards
These cards are quite strong, but not quite as insane. I will put a little less writing into each individual card, and group some together.
Jessica Jones + Gamora
Just solid power cards that can fit into most decks.
Nightcrawler
Can play him into Angela's lane, then move him out, allowing her to get an added +2 proc. Also a good 1 drop, synergizing with prior mentioned cards.
Mr. Fantastic
Good to get power into multiple lanes. 2 power can be enough to win a lane.
Elektra, Korg, Rocket Raccoon, Blade
Good 1 drops. Korg is great when played early. Elektra you almost always want to save until turn6 so they cannot replace the slot. Even if it doesn't kill Ant-Man, it can turn him off in a lane. Blade also wants to be played either final turn, or if you have an empty hand. Note if you have him and Sentinel in hand, playing Blade first means you will discard before a new Sentinel enters hand.
Bishop
Grows with multiple plays, so works well with the 1-drop and/or Sentinel strategy.
America Chavez
She makes you more likely to draw other cards and gives you a comfortable/safe turn6 option.
Devil Dinosaur
Strong card, but not really in the Kazar list, as you empty your hand. You'd want to make a different deck with him (Sentinel still good).
Captain America, Wolfsbane
Best 3-drops for the lane-filling deck.
B-tier cards
Enchantress
Counters some higher rated Ongoings.
Mr. Sinister + Squirrel Girl
M.r Sinister is good in the lane fill deck, esp if Blue Marvel is in play. Squirrel Girl is solid with Kazar and Blue Marvel.
Lizard
If opponent over-commits, win other 2 lanes. You can also just play it late where you can count on it being a [2/5].
White Queen
The main reason to play this is you get information on your opponent's highest cost card on turn5, having a good guess of what their turn6 play will be. Still respect America Chavez, as they will draw her turn6 if they are playing her.
Namor
Threatens a lane on his own.
White Tiger, Odin, Spider Woman, Iron Heart, Medusa
On-Reveal package. This can be a real deck in pool1.
Quicksilver + Domino
The other picks I'll get some heat for. The argument of them lowering your odds to draw "good" cards or "combo" pieces is real, BUT, if you are playing just solid point cards, not missing 1-3 mana can be a huge deal. If you are running the Kazar deck, I'd suggest against these 2, as you are not likely to miss spending mana, but if you are doing a more expensive deck, having early plays can be great (and you can cut other 1/2 mana cards).
Klaw
Impacting 2 lanes is good.
Punisher
Solid vs Kazar/lane fill decks. Nothing too special though.
Colossus
Underrated card. There are enough locations that are negative power (or flat out destroy), that he's solid. Nothing too great, however.
Hulk
Good points, nothing special however.
Concluding thoughts.
So, that's the end of the noteworthy cards, in my opinion. I do not think there's a lot of value of rating cards past that. There are decks that can come together and cards that can be worth playing based on what you open or what you like. Some honorable mentions are Onslaught and Spectrum in an Ongoing deck (or perhaps just Onslaught for Blue Marvel and Kazar), Carnage and Nova as a package, and Moon Girl for our favorite dino.
Movement decks are generally not good, especially Heimdall. When players start to expect movement decks, the math is entirely on the table on turn-6 and Heimdall is often worse than Chavez.
If you have any questions or want any advice, come join the snap.fan community discord. There are often people willing to answer questions and help out! We'd love to have you!