Jump a lot and move right and left. Always go for edgeguards and only use Rollout/Rest if you are really good. Also you should always hold shield, especially against heavies.
Actually just try out combos against Lv. 9 CPUs or actual players with Uair/Dair, Fair chains and Bair spam. Tilts might help but I never tried them to be honest. Also see what moves you can avoid with crouch.