It's pretty overwhelming to scan through the choices Cabela's has and the E.C.W.C.S. Polar Weight has always been a high standard. My much less expensive go-to base layer for all winter is also from there.
For quite a few years now, starting out with the
MTB Heavy Weight Base Layer top and bottom has been the perfect start to whatever number of additional layers are needed and a good middle ground of warmth and price. And half price right now!