That's a good question to ask, and people have had some good suggestions. In particular, I would like to suggest that you work on precision, throttle management, and rudder use, to make your loops round, your rolls linear, and your Cuban 8's & Immelmans, etc, follow a straight path.

Takeoffs & landings that are nice & straight are good practice. The crosswind low pass is good practice. Make it slow, and use rudder & aileron to keep the plane flying along a path parallel to the center of the runway.

Inverted flight, using a high-wing plane with dihedral, is difficult. I recommend it highly! If you master inverted flight, people will notice.

Good luck,
Dave Olson