All the places I trained, we didn't have to use what they sold (some didn't even sell them). But I just don't see anything in the inexpensive uniforms that's not either straight cotton or a cheaper blend. I really liked the uniforms we used in Judo, so I've gone back to something like those (after using the cheap stuff and a couple of more expensive cotton ones). It's like wearing a carpet, but it never feels stifling to me. Maybe I'm just a masochist.Because you have to wear the uniform they give you.
My jujitsu gi is cotton. But the mess around with the weave to make it lighter.