You have such a nice sense of digital art! It's difficult for a lot of people to start digital art. Have you used pencil and paper before? You're doing such a great job for the short amount of time! It's impressive!
You have a nice exploration of colors - I would work on your contrast, though! Use dark shades for contrast.
If you plan to do pixel art, you want to work small and try to make it readable in a small size! It's tricky trying to fit a lot of details in a small canvas. Good luck, I'll definitely post again if you post more work!