I use multiple layers of Smartwool under regular camo. When it gets real cold I start layering camp wool on top.

I have the KUIU 145 weight for early season and the wool power when it gets cold. You can catch it on KUIU clearance once in a while. I love it because it doesn't stink..even after a week in it. The 145 is about the right weight for early season with a long sleeve t or wool shirt over it mornings and evenings depending.

Oh, and silk too. Check Cabela's for the silk. They have a couple different style/weights and I think it starts at about $40 a piece

Just be sure you store it somewhere where moths can't get to it during the summer.  Once I bought some expensive merino wool underwear in the summer, only to have it full of holes when I unpacked it the next winter.  Sometimes I think it comes equipped with moth larvae from the factory, so I freeze it for a while before I put it away.