Thanks for sharing this! I really like some of the ideas you've come up with in that piece - you've done well to create a good baseline and added some interesting layers and percussion section. Well done!
In terms of material, I found that studying a bit of music theory helped me a lot for composing. There's a book called 'Music Composition for Dummies' which helped me (and still helps me) to composed.
Also, learning an instrument and learning to play other music has helped me understand how music is created and comes together. So if you can do this (or continue to do this), I'm sure that will help.
It sounds like you've already got a creative process that is working for you, which is important. As well as focusing on baselines and harmony, I would also focus on what chords work with the melody. Structure and form are also worth considering, and these are things you can learn through music theory.
But the main thing is that you're enjoying it, and as long as you continue to enjoy and learn then I'm sure your music will continue to improve. It's easy to be self-critical and compare your music to others, but everyone is at a different stage so this won't help. Keep up the good work, I look forward to hearing more music from you! 🙂