…like conforming clothing or your own meshes, you may find that the garment doesn’t want to drape nicely but has some sort of “jaggies” sticking out everywhere.
A lot of the time it’s because the geometry is in quads. A simple triangulation operation in any modeler will solve this. But make sure your modeler doesn’t break UVs while triangulating.
And another suggestion contrary to good practices in making meshes for actual rigging: your dynamic mesh should be crazy dense.