Wool for cold weather. Keeps most of its insulation properties even when wet. The best is a good layer system. A good wicking core layer with breathable insulating layers over that and a finale water proof layer. Has to breath to let moisture out. Moisture build up will make you cold. Good hat and socks are a must also. Take off or add layers as needed.
I am just assuming you are wanting cold weather info. Clothing will change with season but with a layered system you can adapt it to the weather.
Under armor as a base layer, poly-pro next, Gortex as an outer shell. Good boots/socks, still have yet to find a GOOD pair of waterproof gloves that aren't bulky!
Base layer, cold weather: Wintersilks silk heavy long john bottoms & Wintersilks silk heavy V-neck long john shirt
Base layer, extreme weather: Eddie Bauer merino wool long john bottom & Eddie Bauer merino wool long john zip-neck top
Main layer, mild to bad weather: Propper khaki public service tactical pants & Propper khaki public service tactical shirt, leather suspenders, leather money belt pants belt, bandana
Main layer, bad to severe weather: Orvis brown herringbone wool pants & Filson khaki original wool shirt with button down collar
Regular weather boots: Danner Ft. Lewis boots
Severe weather pacs: Whites Elk Guide pac
Hat: Akubra Territory hat w/chinstrap, Hat Flap ear warmers for cold weather