I typicly see people throwing out smash attacks, that strategy may or may not wor sometimes on for glory, but it is in no way a good strategy WHAT SO EVER. These moves are very punishable as they have tons of ending lag. Your smash attacks should only be used to punish and K.O'ing your opponent. Your main ways of racking up damage should be your jab tilts aerials and some special moves. One thing you also should not do is roll when it's not needed to, rolling is also very punishable. Also you HAVE to adjust your playstyle after you charcter of choice. For example: A defensive Little Mac who jumps alot and plays in the air is not really optimal for Little Mac, a Little Mac should never really leave the ground, unless he has too. So yeah, you really need know how to play your character to get it max potential.
I sorta want to see how you play before I give you any further tips. Soooo yeah, just VM when you're avalible.