I totally know what you're going through!
I'm going to my first real show this weekend and so far I'm spending $177 and I might end up spending $187 on it. This is all my own money too. (I'm fifteen, so I have to really hold on to what little money I get since I don't have a job yet).
Here's a breakdown of my spending:
$50 horse use and coaching fee.
$10 dollars per class, and I'm doing five classes.
$30 dollars for a pair of chaps.
$35 for a pair of half chaps.
$2 for a BIG container of baby oil.
$2 for a packet of four sponges.
$3 for a notebook just to use for show stuff.
And another $10 because I'm thinking about doing another class. I'm still undecided.
I have everything I need right now, but a few days ago I was getting kind of nervous wondering if I'd be able to get everything by the time I needed it.
Good luck and I hope you get a lot of money!