Leave your cotton at home, and invest in wool everything.
This is very important. Synthetics will also work fine (fleece) for less $ and weight. I have both. Synthetic longs johns, some military wool pants I got at Salvation army and two synthetic layers (not counting the long johns) for my upper body (also from Salvation Army). Consider a thick vest and a light sweater. Top all that off with a warm hat (very important) and you are set for the cold. You'll also need good boots, synthetic/wool blend socks and a wind/rain jacket.
Cotton can kill you
... This may sound crazy but it's true. Next to your brain the clothes you have are the #1 most important survival gear you've got.