Hey, man, don't be putting yourself down. For a beginneer, this isn't bad AT ALL. Besides, if you don't like it, just strip it and redo it like millions of painters have done before you. I'd recommend getting a color wheel for color scheme ideas.
I disagree, I like it, you paint job looks very crisp. The back pack and shoes could use a little more contrast, maybe just a black wash would do the trick. Anyway that's my 2 cents worth