Dithering is risky and can really hurt the presentation of a piece if used approximately. 

I would recommend using real references (photography) in order to better understand volume. It looks very flat here. 

Don't get discouraged! Keep practicing!

Overdithering, weird seperation between light and dark on the pants, anatomy, meh it's not great, not good either. So-so hue shifting.

It's ok for a beginning, however, remember that an essential thing in pixel art is to keep the color count low. Here you have 58, 16 colors would be more than enough. Plus, dithering is a way to simulate gradients with a low amont of colors. With 58 colors, all the dithering is useless and you could have performed a way more smooth render without using it.

Nice design. However, I think  that the dithering is a bad idea. It doesn't really make a good texture nor does blend the colours together.

If you want to train, try a smaller res and lower color count.