There are a lot of things you can do with your trainer. You can learn to take-off, land and fly with precision. You can also practice some milder aerobatics such as stall turns, loops, rolls, inverted flight (to an extent at least). These are all great stunts and its fun to learn to do them well. Work on precision. In wind and without, because flying in wind will force you to use the rudder more to track straight. Once you have a good situational awareness and eye hand coordination you'll be able to fly the wings off a sport model.

To make your trainer a little more responsive you can increase your control throws (just a little at a time) and move the CG aft. Consult your plans/manual about the CG, though, because your plane can become unstable if it is too far back.

As far as inverted snaps. That's ridiculous. You're trainer wasn't designed for that kind of stuff and your just as likely to rip the wings off as you are to complete the roll.

If you want to do snaps get a good sport model that's designed for it. My second plane was a Great Planes Super Decathalon. I also have an RV-4 which ironically, is easier to fly than the Decathalon. Both models would be good for aerobatics.