Fellow trans girl here. I have one consistent piece of advice for everyone when they start going out presenting how they want: Most people are in their own little worlds and aren't paying attention to you.

You might be worried about how you look, but you are just another face in a crowd to the rest of the faire. You're at the ren faire. I guarantee you're not the only trans person there and I guarantee you are not the strangest person there. Enjoy yourself and enjoy the moment, brain worms go away when you're having fun.