Cotton is a very short staple, and needs a lot, and I mean A LOT, of twist to hold it together. Flax is a very long staple, and doesn't need as much twist, and you can spin in wet or dry. Silk usually has a very long staple, and may or may not need much twist at all. They all handle very differently, and there is almost nothing the same, other than you put some twist in each to make a yarn.

I would suggest that you start with your cotton, and stick with it for some time (with 5lbs of cotton, that might be a lifetime!), until you are completely bored with it -- then moving on to something new. All of these fibres will keep you busy forever, I think!! It's all fun!