Our rule is: Above the heart, always on a dress or blouse, but never on an outer garment. This goes for new member pins as well as badges. So you can't wear your pin on a t-shirt or sweatshirt.
I don't think it's specified anywhere what sort of pants/skirt/etc. you should be wearing, but it's implied that it would be in keeping with your top. You'd look pretty silly in a nice silk blouse and sweatpants
so the implicit rule is no jeans, cutoffs, sweats, etc. A nice pair of pants or skirt would be best.
I don't believe we consider a suit jacket or blazer as an "outer garment". I've worn my badge on the lapel of a blazer and no one's said anything to me. If you pinned it to your blouse, no one would see it under your jacket - and unlike some other GLOs, we don't have a separate recognition pin that we could wear instead.