Pick a pair of waterproof
cheap uggs with at least 1,000 grams of Thinsulate. Some of the newer models have 2,000 grams and are ideal for very cold, wet weather. The choice is up to you. The 2,000-gram boots typically cost twice as much as the lesser-gram boots.
Put on wool/polyester blends socks or simply wool socks rather than cotton ones. The right choice depends on your boots. If you opted for the 2,000-gram boots, wear wool/polyester socks; otherwise, use a heavier wool sock. Unlike cotton, even if these socks get wet from your feet sweating, they maintain their insulating abilities.
Put in a sock liner.