Long johns, fleece underjacket, big puffy overjacket. Outdoor Research neck gaiter (never go without it ) Stocking hat--you can even wear a thin one under a bigger one. Fleece pants over the long johns will help a lot, and of course, overalls. Liner socks with thick wool socks, and good boots.
You might look like a big ole puffy santa claus when you're done, but at least you're warm