You can't expect your body to be fully fuctional and ready to go all the time so a real warm up before any sort of workout is vital. It's even more important during these cold winter months. Warm up wear is a great way to start off. Layer that stuff up! Layers trap air in between which warms up and then helps to warm you. You can then remove these as class heats up.
Booties are great for your feet and keep them super toasty even if you have porr circulation there anyway. Plus they feel like slippers and who woudln't want to wear slippers all day long. Proberly more common are leg warmers. These come in a veriety of lengths from ankle height to thigh high, a range of colours to blend in or stand out and usually in a stirrup (with a peice cut out for your heel) or straight. As most classes are standing its really important to make sure those feet and ankles are warm.
Leotards, T-shirts, Cardigans and Jumpers are all great on your top half and as mentioned can be peeled off as you start to get sweaty. Try to get out of sweaty clothes as soon as possible after class. Staying in them in lower your body temprature and they are a breading ground for germs-yuck!