A brief rundown of the Marvel Champions characters based on my experience so far. Maybe this’ll help someone, I dunno.
Captain Marvel: She’s really very good at blasting things in the face. She starts off with lots of HP, and I frequently use her cycling ability to add individual points while replacing cards I don’t need. Deckbuilding should focus on energy, because she has several cards and powers that use it. Has both burst damage and some build up potential.
Spider-man: Jack of all trades, master of hitting villains in the face for 8 damage sometimes. Spider-man is a very versatile character, with damage, healing, threat chasing, mitigation… a lot of choices. The trick is, you only have so much of each of those, so you want to have what you need when you need it. Consequently, I think card draw of some kind will be very useful for you.
Black Panther: Unusual, in that your alter-ego ability is a one time tutor through your deck to get part of your kit, done at the start of the game. You need to choose very carefully, based on your opposition and deck style. BP is also interesting in that he’s rich: his access to Wakanda’s resources give him awesome Vibranium resource cards and amazing cards like The Golden City for when he’s stuck in his alter ego. He also has a very strong 2-2-2 stat line, and a very useful special ability in Retaliate, letting him shrug off stuff like Ultron’s drones. He is arguably the burstiest character as he needs to have his equipment online for him to use Wakanda Forever, allowing him to unleash the beast, metaphorically speaking. Also literally.
Iron Man: Perhaps the most bifurcated character, Iron Man NEEDS to set up his suit as fast as humanly possible. Until he does, he is practically skipping your next turn every time he ends his turn in Hero mode, due to low intrinsic card draw. His suit cards are great, though, and can be used every turn you’re in Hero mode, giving you a real sense of growth and power. His alter-ego as Tony lets you cycle through your deck to find them quickly, which I think you really need to do without delay. Once online, you have truly massive damage potential and flexibility, especially if you stack your deck with resources (was it tech? energy?) for your repulsor rays.
She-Hulk: Wow, she has two amazing natural abilities and lots of HP! I see her as a bit of an all-rounder like Spidey, but I personally like her better. She can slow down or remove threat, absolutely wallop bad guys, and requires very little in the way of setup. Get her out there and start breaking faces!