smartpak has the best prices (smartpak.com) for a lot of attire.
schooling: you can really wear anything, breeches, shirt, belt, tall boot socks, boots/half chaps or tall boots. my everday riding outfit usually is: tailored sportsman trophy hunter breeches, some type of sun shirt (shirt w vents) (eis brand or tailored sportsman usually), a random belt (tailored sportsman, tory, c4 is rlly affordable), some random tall socks, my favs are noble outfitter peddies, & then any boots.
hunter show: show shirt (essex, tredstep, kingsland, etc.), tan breeches (& tall boots) or tan jodhpurs (& paddock boots w garters), a black belt (w black boots) or brown belt (w brown boots)
jumper show: any nice shirt really, again i wear sun shirts for this sometimes, tan breeches (read above), boots (read above). jumpers is much more relaxed w the attire.
and ofc a helmet. if its a rated show it has to be an approved helmet (look it up)
good luck :)
Dover is a good place. Try second hand too. :)
HUNTERS: white pad with saddle, boots not polos and braids (for the horse)
JUMPERS: More relaxed, saddle pad (and half pad if needed), saddle, boots or polos.
Like for shows or for everyday riding? Also, how "fancy" is your barn? Do they have any dress codes? For instance, my trainer would send me packing if I ever showed up in a tank top or jeans lol.
Wear any shirt. For pants wear breeches. For shoes wear paddock boots and half chaps. I usually get my clothes from my barn because they sell tack there. Also try eBay because stuff is really cheap there. Stores like dover are a bit more Pricky but smartpak is in between.
breeches or jeans, tall boots or paddock boots and half chaps, and a helmet. great stores are smartpak or dover saddlery