Translation: Mmmm ... pretty! I only have to add a shell underneath and a cardigan/shrug on top and a skirt underneath ... Essentially, there's no difference.
Yeah, that's totally how I shop. I've pretty much given up on finding acceptable necklines and sleeve lengths in stores and have a nice collection of Kiki Rikis. I don't do that skirt underneath a too-short skirt thing, though. That's stupid. (And yes, I know how ridiculous that sounds considering all the layering I already do.)
I have a post in me about how ridiculous it is that tzniut so often becomes the focal point for girls' religious observance (see the last few grafs of Rav Henkin's article here), and how silly it is that we make this mitzvah even harder by making up brand-new rules of tzniut that have no basis in halacha, and how terrible it is that we judge women who don't follow these communally accepted rules so harshly. But for now, I'll leave it at this.