It depends on the type of weather, but I usually find I'm kept very warm using a combination of Icebreaker thermals, Rohan socks, and an old pair of ski trousers and ski jacket. For boots I use a pair of Magnum Stealth Force waterproof boots with protective toe caps and they are amazingly warm compared with my other boots because they are designed to provide protection against heat - but obviously this works against cold too! I've spent a whole day out there in freezing temperatures with toasty feet in these.
If chainsawing, I find the same, but with Stihl chainsaw trousers are pretty effective. Icebreaker merino wool thermals are expensive, but very thin, lightweight and you can wear them for days and days on end without them smelling. I usually wear leggings, a base layer and one or two mid layers under the ski jacket. The advantage of layers is that you can remove one or more if you get hot, and the Icebreaker ones are very fine so you have no problem of sweating or bulking up. I also use them for outdoor fitness classes.