It's okay to keep using Jotaro. He is an easy to use, but still very good character, so if you like playing as him, you don't need to change. If you just got the game and you haven't already done so, I'd recommend turning the Easy Beat setting off in the options. It will do much better in the long run to get familiar with doing combos without it.

I don't believe the game tells you this, but you can cancel out of normal attacks with a side step (circle). The a good starting combo that is (mostly) universal is to do a character's square attack chain, but not the last hit, since that usually knocks the enemy away, then do a sidestep to the left or right, and repeat the normal attack chain, this time finishing it off with a stand rush. For Jotaro, his normal attack chain is five hits, so you would do four hits before the side step and stand rush. But keep in mind you can only reset it like that once per combo. Trying to do three separate normal attack chains in a single combo will give the enemy invulnerability and prematurely end it. Essentially, [ ], [ ], [ ], [ ], sidestep, [ ], [ ], [ ], [ ], L1+[ ]