M.R.
First of all, I know how it's like to be a single mother and I sympathize with you. I know some people can be REALLY RUDE and if they don't have anything in regards of your questions then don't say anything at all. You have enough to deal with then having to deal with RUDE/UGLY people like that.
Secondly, If it's court ordered as far as your dad goes. He is ONLY responsible for child support, medical insurance and 50% of medical costs that insurance does not cover and that is it. Your dad should buy clothes that stays at his house while his son stays with him and his mom buys the clothes that stays with her. If she choses to buy expensive clothes that her choice but it is definitely not his responsibility to pay 1/2 or all. If he want to help contribute that's up to him. If your mother allows her son take advantage of her and get her to buy the expensive clothes that's her problem. Me personally, If he really wants those clothes then he should start getting a job as he is 16 and old enough to get a job to buy his own clothes. I started working when I was 14 and would buy myself anything I wanted; clothes, going out, etc..
As for you I would contact the attorney generals office or contact an attorney or call legal aid and find out your rights.
Good luck and I hope this helps.
M.