I think generally it's good to build up a strong foundation with more Bach inventions, Mozart sonatas, Haydn sonatas, Clementi sonatas, perhaps other pieces from the season by Tchaikovsky, Burgmuller Etudes etc. You can't really go wrong there, and if the piece you try simply feels too hard, you can try another. I'm sorry your teacher does not support you more, as it would be very good if a teacher could help you out picking some suitable pieces.
Here's the Mozart sonata with the Turkish March, which you may have heard before:
Here's one of the more manageable Beethoven sonatas (still not easy):
Here's a popular Bach prelude & fugue if you want a challenge: