My First Non-X Team: Modify Wolverine's attack value by +1 if other friendly characters on the map possess 3 or more different team symbols among them.

Lunge: When Wolverine is given a close combat action, immediately before making the attack he may automatically break away and may move up to 2 squares.

I am not sure how this trait works... how many characters do I need? One for each different symbol?
All you need is 3 different team symbols. If you need 3 characters to get all 3 different symbols, fine. If you have a single character that happens to have 3 different team symbols (rare, but they are out there), that's fine too. There is no specific character requirement; this trait only cares about the number of team symbols.

Can I use Additional Team Abilities to meet the trait requirements?
No. ATAs do not place any symbols on the user(s) base. The trait wants symbols.

Does Wolverine have to be adjacent to a character in order to use Lunge?
No. You may give Wolverine a close combat action even if he is not adjacent to an opposing character (or other legal target) so long as he ends the immediate movement adjacent to something he could attack.