You need surprisingly little in the way of clothes, but if your route gets icy, you will want to consider studded tires. I wouldn't think dumping in front of a car would make your day.
I am riding on Nokians, they were $100 for the pair at Peter White. First time on ice today, they're champs. Accellerating away from the stop sign on glare ice, sounded like someone dragging an ice pick across the ice.

It was 20*F this morning, snow on the ground, 78% humidity. I'm wearing poly long underwear, poly base socks, wool socks, cheap poly running tights, a cheap lightly-lined running windbreaker pants, then up top, poly base shirt, Wal*Mart compression top, a fleece scarf around the neck once and arranged to cover just the front, and a windbreaker. Nashbar polypro balaclava (5-in-1), and some fleece gloves (not biking gloves, will be replaced, but they're warm). Goggles over the eyes (visorgogs over prescription glasses).

So, two layers socks, bottom, top, then a windbreaker shell, and a balaclava and gloves. I was cozy warm, only my toes got a bit chilly (wearing beat up old shoes in toe clips) but not bad at all. I figure this getup is probably good down to at least 10*F, maybe 5.