Look into some Merino Wool base layers, IMO absolutely the best out there. Very thin and aids tremendously on the layering method, I use it religiously deer hunting and was led to it by some hard core enthusiasts who do a ton of backcountry pack hunting.
You can get it in different weight ranges to fit your needs, Sierra Trading Post - We Are All Explorers. will have some great sales if you monitor the site.

Outer layers I use Cabelas MT050 gear, the rain suit is very reliable and the whitetail extreme bibs/jacket is top of the line but costly.