If you own a pair riding pants and boots, great, but if you don't, a pair of sneakers and not too-tight jeans will do. Most saddles have protective baskets on the stirrups. While you're riding in the round pen, wear something fitting so your body shows because the students usually cheat with their backs and learning lasts much longer.
It's strictly forbidden to ride in the silky sweat pants because you'll easily slip out of the saddle. It's good to get the long chaps because of big friction in the leather, and they're good for snow, you it doesn't wet your pants in the woods. It's also good to have your own riding helmet due to the size, and higiene, altough all memebers of the club wash regularly once monthly.