I love white clothes, personally., but I agree they aren't all that practical. I don't really avoid many clothes other than for style or taste, but in terms of practicality, I'd say I avoid clothes with thick material since it gets very warm here and it's rarely ever cold so it's not really advisable to wear thick clothing. Other than that I just base my decisions mostly on what I think would look good and wouldn't give me too much trouble.
I haven't started buying clothes online on a regular schedule. I have bought a couple of clothing pieces online and I think I intuitively did not consider the ones that are only available in white. I bought different colours, and they are not really hard to clean, but I am not sure that they are sustainable. I didn't really consider many things when buying clothes online.
I try to avoid buying clothes that I'm only going to wear once, I see it as unnecessary and wasteful as well. I try to avoid buying light clothing and also clothing that has lots of holes in it or patterns that might get messed up in the washing machines. I hate buying clothes that need to be hang dried as well, that annoys me to the max. I agree with you when you said you avoid buying clothes that have to be dry cleaned that is also wasteful, I guess I'm a cheap skate or maybe just a smart shopper depending on how you look at it.
I try to avoid buying white clothes, just because I feel like I have to be super careful while wearing them because they get dirty so quick. I also avoid grey shirts, just because I don't think they look good on me, no matter how they're styled.
I avoid sweaters and turtlenecks. I fairly large on top and sweaters accentuate that. I don't like anything around my neck so turtlenecks are out. I used to avoid clothes that need dry cleaning, but I tend so gravitate to those clothes so I gave in. I avoid wearing jeans for most of my childhood. I wore them in college. After college, I stopped buying them. Even now, I don't own a pair. I also avoid pants in general. I find them to constricting. I much prefer skirts and dresses.
