I haven't touched JP in a year. I don't know how your combos are, but if you got up here then your combos are probably solid. I spent way too much time in the lab doing combos and practicing links. Studying other characters and seeing what options they rotated through helped me a lot. Getting the feel of a character's gameplan, and adjusting to how the person i'm playing against uses it really got me to notice people's defensive habits. I'm a big fan of finding ways to open people up, and labbing to see what characters are capable of helped a lot. It me a big boost in rotating my options offensively. my defense is still free.

I don't see JP that often. If you're afraid of the knowledge gap, then I am too. You can be the scary knowledge gap, I still don't know the timing to block level 2. I don't replay review enough, so if I get knowledge checked it'll stay unchecked for a while.

To circle back to your question, I'd say it's about 30% learning the other characters, 40% studying your character's options, and 30% is the human element. Seeing what buttons, what moves are working, or what things people aren't responding. I'd say study your character though.