I have very nice, cute clothes for trying horses out, having someone come out to try my horses, and “barn girl days” when we go to big shows to watch or audit clinics. I also got them on sale. They only see horses when the horses, stalls, and tack are already clean. :lol:
If I’m schooling in a western saddle I’ll wear jeans and a tshirt. If I have an english lesson I’ll have a fitted polo tucked into my breeches with a belt. I don’t like wearing baggy tshirts when I’m riding because it’s easier to actually see my position when it’s more fitted. That said, my friends with the $60 polos absolutely LOVE my bright colored, well fitted, $5 Walmart polos. 
If I come out to work there all day you better believe I will be in well used athletic shorts and an old tshirt. :lol: Dress great for first impressions, but if you’re there to get sweaty you will get tons of laughs in your $75 polo, $50 belt and $400 pants.