I'd rather be too warm that too cold, I can unzip my coat and be cooler in a few seconds, but if I under-dress getting warmer halfway into the ride is not easy.
The base layer that I start with come october or so is-
Skinsuit of choice (I buy these cause they are about 1/2 the price of a good jersey, and they last me about 2 years or so for the most part, I currently have one for each day of the week, and when they start to wear I hit Ebay and start looking for any that are under 40 bucks with shipping, it usually only takes a week or so till I have the one that's wearing out replaced)
Windfront Tights - Nike
Polypro balaclava
full finger gloves
shoe covers
Then when it drops to the 30's / 40's
I add Columbia jacket
Arm warmers
Ski pants
Then below 30
Columbia jacket liner
windproof balaclava
100G thinsulate gloves
So far I have ridden down to 16 F, my pinkies got cold, but that was about it, so I am trying a pair of heated gloves hoping they will take care of that issue.
I have vowed to not pack on 20+ Lbs this year like I did last year during these months, so far I'm up about 3 lbs, but with only two weeks to go till Christmas, I think I'll be ok as long as I stay on the Pedals.
Joe