Get hulk and torch, Spider-Man is going to be nerfed to uselessness and is in no way a good investment anymore. A lot of us have him already, and he is now marginal. Invest your ISO and HP elsewhere.
No love for Doom? Doom was one of my first 3*'s over level 60. His black power when maxed will be a very nice addition to starter’s roster. At aprox level 60 and 4 black covers he will add 600 damage each attack until his strike tiles are destroyed. I don’t use his as much now but he was very instrumental in getting to where I am now.
If you’re a new player then I recommend spending some money on roster spaces. That’s the ONE and ONLY thing in this game that I think it’s worth spending money on.
If you really refuse to spend money then I agree with what others have said.
1:Hulk Black
2:Human Torch Red
3: Doom (Because lightning rounds)
4: Spiderman (There is a chance that after the funbalance he’ll be featured more, but that’s a big IF). Spiderman has become a bit Taboo.
Buy Roster spaces, keep them all. You WILL need the heroes at some point for character required nodes, and they will be buffed or used in restricted events.