Wario vs. Smaller Characters?

[RunningEXE]

I understand that some smaller chars like Mario are a bit easy to kill as long as you get them off of the stage, but i'm having an incredibly hard time against people like Pichu, Pikachu, Mario / Doc. (sometimes), etc.

What is the best approach when going after players with small character hitboxes? I can rarely land n-air combos, so should I try and attempt f-air / d-tilt combos? It's just difficult playing against super aggressive players. Any help is appreciated.