It looks nice! I just think that you should try to make the lines and edges a bit smoother, because the lines look slightly choppy. Other than that, you should look at references and maybe watch some art tutorials. Practicing also helps! Hope this helps a bit, i'm not the best at giving criticism 😅
Uh- I don’t think that’s how it works? I think you’re supposed to start with white gems, and every time somebody finds something, they get a colored gem.
or I’m stupid and you’re doing it perfectly fine