I was riding outside the last few years down to around 40 or there was snow on the ground. Any colder, and even in the 40s and 50s, my hand starts to hurt due to some nerve issue. It usually passes once I really get going but it can really be painful until it does. You need to have layers so that you can shed them as you warm up. I live near Prospect Park and almost every ride goes through there and when I climb the small hill for the first time I warm up. Full fingered gloves, leg warmers, lightweight synthetic long sleeve undershirts, long sleeve jerseys, a windbreaker jacket are usually enough. Booties are mostly unnecessary unless it gets really cold or you have cold feet. I've only once or twice worn a hat under my helmet and it was always too much. I have multiples of each and I mix and match depending on the temps. When I was still commuting I would have to make sure I had enough for later in the day too and more than once I didn't. And if you wear street clothes just remember you'll get damp, and cotton just stays damp. Damp and cold is just not fun.