Honestly? Time.
And lots of hours both playing and watching others who play your character. Don't be like me and focus on long ass combos only, it looks great sure but if you caught up on needing to hit it in a match the preassure might cost you the game as it does for me lol.
You play Cammy, so focus on your reactions what we call hitconfirms. Drill into your soul when to spiral arrow and when not to. Fish for Spiral Arrow if you can get two crouching MP's. Anti airs also, but if doing dp on reaction isn't 100% working out at the moment then keep it simple. Back MP.
What you said about chipping away their hp is no bad thing, risking it all and getting punished sucks. Try and punish those who throw out a lot of specials, easy dmg and it all racks up.
Don't forget to use her vtrigger, you can easily extend a combo.
Keep em in the corner with jab, crMP and lk preassure, DP them when they try and jump out, you have the advantage on what they are desparate to do. Which is to jump out if they have no teleport or EX move to shift position. If they do have bar some may well do just that so be careful.