Dress too dark. Not enough detail (I understand it's a black dress with no real detail per se but the texture is lost)
I really like your eye and composition but the product emphasis needs to be numero uno in fashion.
With that said, I think the first shot is really your best here. The second and third have artistic merit and show the CUT and DESIGN of the product but no texture. The last shot is more of a beauty shot than a fashion shot.
Overall, I like where you are and this of course is just MHO.