Looks nice! You could try taking bounce light into account, it seems complex but it’s not that bad. Instead of going lightest closest to light source, darkest farthest from the light source, have a light side that gets darker farther from the light source, a core shadow, and then a dark part where that’s just a little lighter than the core shadow. Also, practicing cell shading is a helpful way to get used to figuring out where the core shadow would be, though it looks like your goal is to draw in a realistic style so it might not be as useful.