I ride in the cold. I've done work commutes down near zero deg F. One I remember was seven degrees. I think there've been a few others where it was colder. Maybe I've hit zero. Or close, anway.
For my feet, I use these:
I also put my bare foot inside a plastic grocery sack and put a good wool sock on over top of that. The good thing about this is that my feet still sweat --that's gonna happen no matter what-- but the sock stays dry. And that makes a huge difference. If it's really, really cold, then I might put a grocery sack on over the sock. Between the inner plastic liner and the outer boot cover, it doesn't matter what boots I wear. Anything will do.
For my legs, I use these:
In mild winter weather I'll wear sweat pants underneath. If it's getting cold, then long johns plus sweat pants. And more can be added in if necessary.
For my hands I use home-made Bar-Mitts. These allow me to ride in brown Jersey gloves in most weather. Sometimes some ski mittens if it's really cold out there.
For my face and neck, I use these:
My helmet is a basic bicycle helmet with the holes sealed up with silicone, making it waterproof. I also attached a bill with a clear face shield attached. The face shield is cut down so that it goes down to about level with my nose, but no lower. The reason is that it'll fog far too much if it's any lower.
I also recommend something along these lines:
I recommend them especially in winter. There are simply too many motorists who get all flustered when they come upon a bicycle at that time of year. They threaten to lose control and slide into you. You need to make them pay attention and this'll help.
Soon I'm going to try a mod. I'm going to take an old sweatshirt and cut it off an inch or so below the armpits. The reason is that I tend to dress as light as possible. To avoid stiffness. And I've found that my upper arms and shoulders tend to be the part of me that's closest to being cold and uncomfortable.
It wouldn't be all that hard to simply add another layer. But then my midriff gets bulked up on clothing. So I'm going to try a cut down sweat shirt. Hopefully it'll give the shoulders a bit more cover, but it won't feel as though my belly and waist are in a straight-jacket.