first of all its an insult and means something along the lines of you're not worthy to be alive or just that you're unappreciative of something and unable to reach your full potential, or in this case not worthy to have skin. for insults like this you need to pay attention to the situation and the surrounding conversation cause they vary.
you might get you're a sorry waste of an education (if you don't do well in school)
You're a waste of air
or simply you're a waste