Key thing is to not overdress. Think of what it will be like after 10 mins on the bike. You'll be generating lots of heat and will probably be comfortable with less clothes on. Go out wearing a little less than you need and you will adjust to it quite well.
Here's generally the temps and clothing I wear when it's sunny (adjust by about 5-10 degrees when winter/dark):
50+: shorts and short sleeve shirt
40-50: full fingered biking gloves, long sleeve shirt, long windproof pants
below 40: windproof jacket with pit zips open, ski gloves sometimes, balaclava over ears and head.
Even below 20 degrees, I just add a wicking long sleeve shirt to the above. I've yet to be in any temps below 15, so I can't say.
You need to see what's comfortable for you. The above works for me.