All my fabrics somehow fit into a sustainable source. I can get them in different levels with different labels. I try to avoid mixed fibres. They can be cheaper, but they are harder to break down. I’m also not a fan of plastic fabrics (polyester, acrylic etc.)
Wool is a natural fibre made from the hair of sheep, goats etc. Wool does not need to be washed a lot. Airing it is the best thing to do. If you really must wash it, do this in cold water with special soap for wool. Wash it very gently, or it might felt in a way you don’t want to. Dry it flat, after squeezing excess water out by rolling it into a clean and dry towel. Store it when it is completely dry in a cotton bag with cedar wood balls or dried lavender to keep the moths out.
Linen is a natural fibre made from a flax plant. It’s a bit harder then cotton, but it is stronger and goes softer after each wear and wash. It can wrinkle a lot, but that is in my eyes a charm. The making of linen costs the environment a lot less than the making of cotton. You can wash linen hand-warm (30-40 degrees Celsius) and, depending on the garment, in the washing machine. Dry hanging or flat and iron it on medium heat. Using steam is alright. During storing, new folds and creases can appear, so I can advise you to iron it again before use.
Silk is the spinning thread from a moth caterpillar. It comes in various weaves and is very strong and long lasting if treated right. Wash as little as possible. If it can be washed, do so in cold water with special soap. Hand wash with a little bit of vinegar to restore the shine. Dry it flat, after squeezing excess water out by rolling it into a clean and dry towel. Don’t let it dry on wood.
Cotton is a plant based material. It is usually soft and cool for the skin. They make perfect bases and undies for costumes, since they are easy to wash out. Cotton was not very common in historical clothing. If it was there, it was expensive. You can wash it up to 30 degrees Celsius. You can iron it after drying them flat or hanging with steam if needed.
All others fabrics
I still have old stock with polyester or acrylic in it. Throwing them away seems rather stupid. I’m phasing it out by using it. All new fabrics I buy are biodegradable.