Layers. Also: If you're warm when you walk out the door, you're going to overheat a few miles into your ride and spend a couple hours stewing in your own sweat, feeling clammy. It's gross and not the way to deal with winter riding.

Wool makes a fantastic base layer. It wicks pretty well, dries pretty quickly (not as fast as synthetics but much quicker than a lot of fabrics) and keeps you warm and feeling dry when it's wet.

How much insulation you need depends on how cold it is.

If you get dry winters, pick up a down vest. You can get one pretty cheap if you shop around, mine was $35 at Costco. Doesn't need superb quality. It should fit into a bottle cage in its stuff sack. On really cold days, it goes on over your jacket.

Hands, feet, and head really depend on the person and the conditions.