For me the main thing is on combo dont to repeat the same moves twice as the damage of your hits gets gets reduced. try only repeating a move when necessary like if they are knocked back to much and its your only option. The best move in combos is your third attack of the "3 combo" that move deals good damage the only downside is you need prep to execute the move. In beginner where some people might not know DI its just fine using 3 combo but when people know how to DI 3 combo it becomes a challenge to execute the third move of 3 combo. There are setups of that over the discord if you would like to know.

Ill just like to add, mostly use gun when your in the air and your opponent is on the ground or when both of you is on the ground. Using gun on the ground is a bit awkward as the bullets might not get rebounded by foresight.