Your art is really cute! However, there are some things that seem like they were done without a clear purpose. For example, there are four highlights in the hair. Assuming this is moe/anime art, it is good, but highlights are only in the place where the light hits brightest. The shadows also don't seem to have a clear place they're coming from. I would recommend picking a single light source and basing your shadows off of that. For example, if the lighting is on top right, the highlight of the hair would only be on the top right of the head, and the shadows would be everything that isn't being hit by that light, like under the bangs. The image I left here shows it better than what I can explain.
I don't recommend shading with just an airbrush. The lower body/neck part you did good, where you used both soft and hard edges, but the head is shaded exclusively with airbrush/smudge tool, and it makes it seem muddy. The airbrush isn't evil, but it should be used with caution. Same goes for the smudge tool.
I like the eyes, and the character design is cute! Keep doing what you're doing, practice is the vital thing!
