Since this is a hunting forum I'll give advice leaning more towards a hunters needs than work. A lot of this advice also comes from backpacking experience.
Several light layers are much better than 1 or 2 thick layers since you can adjust to different levels of exertion. I always carry a daypack to keep gear in.
Cotton kills. I never wear ANYTHING made of cotton when outdoors except in hot weather. Spend anytime outdoors and you are going to get wet, either from precipitation, or sweat. When cotton gets the least bit damp it sucks the warmth right out of you. This is why it is a great hot weather material, keep it wet and it cools you as it evaporates.
I haven't owned insulated boots in years and have hunted in temps down in the single digits. If your feet get cold it is because your body's core (internal organs, and brain) are cold. Keep your core warm and your body circulates blood to your feet keeping them warm. Let your core get cold and your body shuts off circulation to your feet in order to send more blood to your core and keep it warm. I just wear good wool socks and quality leather hiking boots. I've found my feet just sweat in insulated boots and when my feet get damp it is impossible to warm them even with insulated boots.
Keep your head warm. I've found that by wearing facemasks, watchcaps, (often 2), and neck warmers when not active My feet stay much warmer. I see hunters in the woods all the time wearing 1000 gram insulated boots, insulated coverall's and a thin cotton ball cap. They complain that their feet are still cold and they need better boots and coveralls. When I tell them their money would be better spent on something to keep their head warm they will tell me their head isn't cold. Of course not, their body is diverting blood from their feet to keep their uncovered head warm.
I typically wear wool socks, (don't even think about anything else) several layers of lightweight polypro or wool tops and either a wool or insulated jacket or vest depending on the conditions. I usually use a synthetic fill jacket, but if there is zero possibility of preciptiation I may go with goose down to save weight and space in my pack. The newer type of wool military issue gloves with gripping dots on the palms and fingers are perfect for my hunting needs. I almost never wear long underwear bottoms because they would be too hot to walk any distance in even single digit temps. For working, or if my hunt only involved a short walk then I'd wear them. Polypro or wool only. No cotton. I use another pair of lightly insulated windproof pants that can easily be slipped on over my pants once I get where I'm going. Some type of lightweight wind and waterproof shell jacket that is big enough to cover everything else is critical, but rarely used.
If it gets really nasty I have a lightweight backpack sleeping bag that weights 2 lbs and is about the size of a loaf of bread that goes in the pack. I can get in it and zip it up to my waist and be comfortable in some pretty nasty weather.
