I thought I'd do a quick edit:

Maybe you could do a more relaxed stance?

I changed your style a bit, and you were wasting a lot of your colors. Such has, the string on the hoody looked like the same color as the jeans, but it was just a little bit different. And you could double the color on the shoes with the hair color. When you shade, the shadows should slightly shift hues towards a colder color, like blue or purple, and when your adding highlights, shift towards a warmer color like yellow or red.