The legs are too long and the head is too big. Also the whole face is too small, (or at least the different parts are too close together) and looks flat.
I think you could use some anatomy references for checking the average sizes of the different body parts and apply them on this piece.
And uhm, looking at clothing (for folds mainly) could help you.
The coloring could use a lot of work too. The blues you put in the hair stand out too much and look out of place.
Overall the piece looks too jaggy and the AA you are applying doesnt work because the colors you are using for it are too light to buffer at all.
Right, Hopefully i addressed the anatomy issues mentioned (legs, head, face), I also tried some more realistic shading on the shirt. I'll redo the colours and AA when i get home abit later. (this computers MSpaint cant replace colours for some reason)

Looking Better?
keep in mind that this is
ment to have abit of an animesc style to it. though thats still no excuse for bad anatomy.
Edit:

I normalized the colours which felt abit sad. But i think the image looks better for it.