The things to invest in that can make or break a hunt: Good boots that don't make blisters and don't let your feet get wet. Good long johns (polypropylene) that wick moisture (NEVER use cotton), good rain gear (packable is what I prefer. Wear other clothes to keep warm, just cover them with raingear when needed. A good sleeping pad (or cot) and a warm sleeping bag.

If your feet hurt, if you get cold and wet, if you are cold at night, you will be miserable.