I like to buy nice quality outdoor specific wear, but not bike-specific stuff. For my uses, regular outdoor gear works best. Cycling specific stuff is good if you are using it just for cycling (except gloves-cycling specific winter gloves suck in my experience). If you're looking for one piece to start with, I'd say that a nice windproof jacket would be my first pick (assuming you already haveany kind of winter hat, gloves & shoes). Second would be a balaclva. I use a Mountain Hardwear Windstopper Tech Jacket when it's really cold (although take my recommendations with a grain of salt, I don't ride once it snows) It's windproof, so it allows me to keep very warm with regular layers underneath. It has pit vents so I can regulate heat, and it's not too expensive (you can find them for $100 if you look). Along with regular winter gloves (Just those thicker ones that you'd get at any department store), a hat, balaclava & windproof shoes (I wear goretex nike running shoes but anything that blocks the wind will work for a lot of commutes), and I can stay warm enough for most temps that I will ever experience (Cleveland).