This is a really good piece, and the eyes and hair look really nice. However, the neck is wider than it should be and shadow on the neck is black. ( dont shade with black. use a color that matches the skin tone.) The anatomy needs work, as the shoulders and collar bones look a little off. (for this, I'd recommend a reference. they're very helpful!) You drew the face really well, but I think that you should focus on improving your anatomy. Try doing some anatomy studies, as those would help. Another thing would be the colors. When you shade, try using colors that are a slightly different hue then the original color.(example- if your character has peach-colored skin, use a reddish peach color to shade.) This will make your piece look more dynamic.
I'd recommend that you try to work on your anatomy, and that you focus more on the colors you choose. But the things that you did well- the face and hair- look really nice!