If you use a decent polyester satin and cut straight, you shouldn't need to do anything to an edge that is going to be enclosed. I never had any trouble when I was making prom dresses and wedding dresses. Acetate satin is a different story, but I wouldn't use it for anything that was going to be laundered anyhow. I assume you use at least two rows of gathering threads (I like three) or gather by zigzagging over a thick thread and handle it as little as possible. Slipper satin is heavy for anything gathered and charmeuse is very light with little body. My recommendation would be the poly from JoAnn's - at least what we sold in the 90s.