Joe has it right.
Working outside is challenging because you might have periods of high exertion followed by lower exertion. When dressed in layers, you'll need to shed layers during the high exertion and put them back on later.
Having a lot of experience in winter camping, my suggestions would be the REI/Northface/Marmot route. As joeinwv said, get a base layer, usually a polypro blend of some type. These are very good at keeping a little heat near you, and wicking the water away.
After that, I'd hit a nice zip-up fleece jacket (and pants for the sub-zero days). After that, a down or synthetic jacket. Finally, a good Gore-Tex or other breathable shell.
As you warm up, remove the outer layers and put the shell back on. If you're really exerting yourself, you might just have the polypro base layer and your shell on.
Use fabric known to maintain insulative quality when damp. Wool is a natural way to do this, as are a myriad of synthetic brands out there. This way, even the sweat vapor your body emits will not cause insulation reduction. (Sweat vapor usually condenses into water as it reaches your shell layer).
Lastly, get a pair of Expedition weight Smartwool socks. You will think I am an idiot when you see they're around $15. I am not an idiot. These things are one f the best valued pieces of outdoor gear I own.
True story:
I went to Michigan Tech, way up in da UP, eh (Michigan's upper penninsula). I was cross country skiing with a girl (she was literally a professional at this and after graduating went on to compete at a national and international level). I had my big green goosedown parka on because it's cold out. After 45 minutes of trying to keep up, my parka was soaked. Being in -10F weather with a soaked goosedown parka SUCKS. Next time we went, I left the parka in the duffel bag and had on a wool sweater. Upon finishing, my female friend had my parka out and ready for me. =)