I can actually understand the restrictions on colors of things for your horse, like your schooling pad and sheets. They want your barn to match and represent the barn. If you are showing rated shows I don't think this is uncommon. Still sucks though, that you have to buy all that all at once to start. Maybe you could talk to your trainer and explain that your budget isn't quite up to everything at once, and ask what things are most important to get first, and build up as you can. Maybe you can borrow a couple things for the first shows (ie saddle pad, dress sheet to get to ring) so that you can still match.
What I do see as a problem is requiring certain brands. Not everybody fits the same brands as well. For example, lots of people prefer Ariat breeches to TS, and they are perfectly acceptable for the "A" circuit. And helmets, it's well known that different brands and models fit differently - and really proper fit should come before proper fashion. The list makes me think the concern is more for fashion and trends than overall turnout. I don't think it should matter if your stuff is quality and fits well.
In any case, get thee to eBay