Goose down is very warm but can be bulky... Long underwear are great. I have an old snow suit but I dont remember what its made of. Wool socks are a must. Lots of heat comes out of feet. The little heat packs that you shake up are amazing. The ones they make for feet I find to be to hot.(like burning hot) so I use the hand ones and tape them to the bottoms of my socks. Look for Thinsulate insulation in clothing.