In practice mode, grind combos, block strings and reacting/hit confirming to aerial CHs and guard breaks and guard crushes. You can also practice comboing from moves from different distances (2b from 1 character length away, 5b from 1.5 character lengths away, etc) and work that into your muscle memory. Once you feel you have a solid enough grasp on the basics of your character, you can start working on damage optimization, fancy mix up, etc.
If you want to feel more competitive in matches, you can use simple combos (things you know you can hit 99% of the time) and instead, focus your spacing, movement, mix up, oki, hit confirming, blocking, and yomi.
If able, record your matches and watch them. It lets you pick up on your bad habits, and you'll be able to more easily see patterns and holes in your game play.
Also, ask for advice from better players after playing long sets against them. They should be able to offer you some advice, either about the match up or issues they've noticed with your game play.