Some observations on different fibers as relates to needlepoint:
Made by bugs. Shiny. Impresses people. Can be VERY thin if you want to be embroidering tiny things, so it’s good for stuff like petit point. Expensive. Very “shreddy”. Damn stuff falls apart if you’re much rough with it. Hard to come by and so can have limited colors. But it is very shiny, made by bugs, and impresses people. So it’s your choice. Also it takes some care with washing. Doesn’t handle high heat well.
Dull. The dull is NOT a drawback. Sometimes matte is what you’re wanting. Traditional. Employs sheep, which can later be made into soup and scotch broth is tasty. Lasts forever if you disregard moths. Reasonable selection of colors available but it will require ordering online or going to a specialty shop. You can also obtain bits of it as cast offs from knitting friends, who usually have little balls of the stuff lying around. Also you can get it in various sizes and huge amounts, if knitting wool works for you. You need to be careful washing it but it blocks amazingly well.
Cheap. Medium shiny. INSANE numbers of colors. Easy to find. Holds up pretty well, but not to daily use, so upholstery is inappropriate. Feels nice and smooth. Easy to clean. The large companies making cotton floss have good control of their dyes, so you don’t need to worry about dye lots, which means you can just pick up a skein or two if you run low instead of having to buy far more than you think you need and be left with extra threads lying about.
If your’e okay with it, pretty much any fiber is useful. Knitting castoffs are amazingly useful and easy to come by, although it does mean the embroidery will have a large stitch size.