Wool for all layers. Merino wool is excellent as many have previously here stated. A lined wool shirt for mid layer and a lined wool vest for outer layer. If it's brutally cold a Mackinaw coat cannot be beaten.
LL Bean has lined wool shirts and pants.
The Buffalo Wool Company has gloves and socks made from a mix of Bison down and Merino Wool. They are expensive but very warm.
Gost wear in Canada has very good wool clothes at the most reasonable prices.
Stormy Kromer hats are great and come in a wide variety of colors and configurations.
I began wearing wool about 13 years ago. It is vastly superior to man made fabrics.
It is warm.
It is extremely durable.
It keeps you warm when it gets wet.
It dries very quickly.
It is fairly water repellent.
It wicks away moisture from your body.
It keeps you surprisingly cool as temperatures rise.
It is the quietest material there is. Man made fabrics are noisy! The fabric makes noise every time you move or anything brushes against it. If you have been wearing man made fabrics, you have become accustomed to it and you will be pleased greatly by the silence of wool.
Whilst wool garments are available in camouflage, there is not a wide selection. I quickly learned that camo is for man's eye. It is utterly unnecessary. To me, it has become cheesy and trendy looking. Traditional wool hunting clothes in green, red, black, or gray are all one needs to blend into the woodlands. Think about it, game animals blend in perfectly without sticks and leaves printed all over them!