My dog doesnt do tricks.?

I have a American Bulldog and no matter what he wont do it. I try to use treats but he just takes them from my hand. I cont afford to send him somewhere where they will train him or teach me how to train him. ive been patient and i don't lose my temper. For example, when i try to teach him paw he wont let me grab his paw. he nibbles my hand then runs away. The only thing he can do is sit. Any help.