character animation

I am sorry, I do not quite understand what you are after, so here are some suggestions that may or may not be relevant!

If you want the wave pattern to be changing I would decide how first. For example cycle layers allows you to draw a sequence of images to animate the waves rolling along. Or if just swaying backwards and forwards then maybe you want the waves as an independent layer attached with a weld joint on the bottom edge with sticks and pins along the bottom edge to keep it attached to the dress. (pins anchor a layer to the parent mesh)

If you want the main dress to also sway, then think of the dress like clothes. Create an independent layer for the clothes and attach to the body near the waist (or lower) and put some pins and sticks to attach to upper legs. Pins stop movement relative to parent mesh. Sticks stop warping so you could put a stick on the dress near the legs to stop it warping too much. But it will only move if you put dangles on it, which has gravity etc settings to also control degree of warping.

Where it gets fun is trying to do a dangle dress with cycle layers on top! Never tried that combination. Would have to try it and see how it works in practice,