sasuke-kun.: I would suggest looking at my site (in my sig). It has a general strategy for the top 4 in the game. (storm, sent, cable, mag)
Resets = A combo following another combo or an Infinite in order to A. Reset the damage meter. B. Confuse your opponent.
A quick example - c.lk + psy AAA, c.lk, (psy hits), OTG (on the ground) c.lk, c.hk, hyper grav., c.fp, sj.hk, ad/df, sj.lk, s.lk, Dash under opponent (reset starts, combo stops), c.lk + psy and then a combo of your choice.
Magic series = launch, sj.lp, sj.lk, sj.mk, sj.mp. (I almost ALWAYS say it like this though. sj.lp, sj.lk, sj.lp, sj.lk, because it is assummed that the second sj.lp and sj.lk are medium attacks.
Teams are ONLY based on your favorites if you play the game just for fun. Most teams are based around these characters:
Magneto, Cable, Storm, Sentinel, Capcom, Cyclops, Doom, Psylocke, Strider, Black heart, and sometimes spiral.
^ Those are the best characters in the game.