The piece in whole sounds ok, perhaps a bit repetitive because of the rhythm, I know you focus on modulation.
There are many..... many ways to modulate, I know the following:
- Diatonic pivot chords
- Chromatic pivos chords
- Direct modulation
- Without harmony, by phrases
- Chained dominants
- Pivot sections (circle of fifths)
- Sequences
- Enharmonic modulation (augmented sixths, bIII+, dis7)
- Mediants
- Related chords
- Lydian chords
- Neapolitan sixth
surely there are more ways