Pretty good, I think the main thing you could try in your pieces is chords, working out what sounds good, and what notes go with what. It's what I base all my tracks off.
Try using the notes Bb/A#, C, and D. You can also use notes A and F, but use A as a lower for a darker tone at the end of a repeating chord pattern, and F for a higher, maybe to increase tension. Check some of my piano pieces, they use these notes (and their respective transposes) a lot.