I have leotards and skirts from a dance store I use for practice once in a while (and my first tests) and after a year of skating got my first real skating dress--it's definitely different and I'm glad I wore it for a lesson today before the test next week. It helps to get the feel for it, and it does feel different! I also tried my new overboot tights and I LOVE the Mondors with velcro closures--they're warm and they don't slip up the boot.
Jeans--well, there's one guy at my old rink who does skate in them, and he has all his doubles. They seem to work for him, but I have to admit all of us raised an eyebrow the first time he wore them. I would think they'd have to be soft jean material rather than anything stiff. But everyone where I work wears practice dresses, tights, or warm-ups of some sort. When I don't wear skirts, I wear inexpensive warm-ups over a leotard and tights, and sometimes an extra shirt over the leotard.