Honestly, wait for them to come to you. If they jump do iag or jump1 for the bounce and juggle opportunity. I think converting combos from enemies who constantly jump is going to help cassie's game a lot. I also like to mix them up with 33+nut punch or 331 so when they get in they have a 50/50 to guess wrong, if they do at least you opened them up for some damage.
D4 them even if they block you can advance with b12 and go into a 242, b12 kick flip combo you're comfy with. If they block do b121+d14 (caged rage) +mb the gunshot for the insane chip damage and If they block entirely too much then grapple to throw them in the direction you want so you can get them to that corner asap. You can also finish off combos with b124 instead of nut punch, it throws them hella far and is a good rush down tool.
That's really all you have to do with cassie.
Oh and don't be shy with the f34, it's an amazing overhead (18% damage) to open up an oponent that's blocking ducked.