Crouching Light Punch is a fast move and is a good combo-starter. It can combo into itself or into Crouching Light Kick easily.
Crouching Light Kick is a fast move and good combo-starter and can combo into itself or into Crouching Light Punch easily. One interesting facet of this move is that you can combo from Crouching Light Kick into Oni's Fireball. It takes some timing though, so practice.
Standing Medium Kick is a pretty good anti-air.
Diagonal Jump Medium Kick is one of Oni's cross-up attacks and is very useful as a mix-up tool. Like any good cross-up, it is easy to combo after a successful attack for big damage, so find a good bread-and-butter combo to guarantee yourself good damage if you hit with this.
Crouching Heavy Punch is a great anti-air. It has pretty fast start-up for a move of this type, making it very quick. Make sure you still practice the timing, however, as it does have considerable recovery time if you don't time it correctly.
FORWARD + MEDIUM PUNCH
With this move Oni does a two-hit overhead chop attack which, as you would guess, is his overhead move. As always, this move is useful when your opponent is crouch-blocking a lot. Just be sure to use it when you think your opponent will not expect it.
FORWARD + HEAVY PUNCH
Oni's Forward + Heavy Punch is pretty useful in that it can actually negate many projectiles. It's also relatively safe on block and has decent range.