I always use sport shirts, adidas, under armour, etc. I sweat a lot and most equestrian shirt don't keep me cool
Tailored Sportsman icefil sun shirts! They are long sleeved but super cool comfy and breathe able!
Ariat sun stopper shirts really help
I know that there is riding tights that are like leggings I know carrots and ovation have several types
I honestly love just plain ol' Nike and Under Armour
My baker pants are super nice and thin matirial, great for hot weather
Bare equestrian are the best
Smartpak and Dover Saddelry have a few styles of moisture wicking shirts.
The Kerrits jods keep me cool they are very thin, kind of like leggings, they are just really expensive.