I suggest LLbeam or other polortec/polyprob base layers(
www.llbean.com/llb/shop/887?nav=ln-27&pa...-underwear-baselayer
). Underarmor's cold gear is also very good. I think wintersilks are crap, They are OK for fall and the beganing part of winter but once it drops below freezing, they're not really effective at all. They are more effective for men then they are for women as a whole also score very low on cold resistance testing done by bv. Which to me makes them unacceptable.
I also suggest buying good warm wool sock. ones designed for being outside in for cold for longer periods of time, think winter hiking/shoe boarding socks. Feet are very important and frost bite is no fun.
Please get a nice solid ig looking hat, you'll need it to stay warm.
As for costuming aim for wool, wool blend, of a fleece(which is polyester blend usually) you can get patterns at joann, simplicity.com or mccalls.com. Online they usually have really good sales. Malls was/is running an all patterns $1.44 each sale.
hope that helps.