https://www.ethicalconsumer.org/fashion-clothing/choosing-su...
It's definitely complicated, but their take was:
* Best: second-hand, recycled, or organic
* Middle: lyocell products (Tencel and Monocel), linen and hemp, followed by Modal, acrylic and polyester
* Worst: conventional cotton, non-lyocell viscose, rayon, elastane, nylon and wool
OTOH, I would argue my wool items (t-shirts, underwear, as well as larger items) don't need to be washed nearly as often, and especially in comparison to cotton (an environmental disaster in most ways) t-shirts, they last a lot longer.
I dunno, I try to avoid cotton, rayon (et. al.), "bamboo" (mmm, not really), and the see-through shit you get at the mall. But I've got to wear something, so that's about the limit of effort I'm willing to put into it.