In winter I fimd that the main enemy is wind. Where I live it gets really cold, so I only bike when it’s above -15 celsius. Even then, pedalling keeps me warm with just a thin wool or polypro undershirt, a thick fleece jacket, and a REALLY windproof shell. Windproof mitts over thin fleece gloves. Nice thick pastic bags over my toes inside light hiking shoes, wool socks. Ordinary winter tights for the legs, but on the coldest days I put baggy mtn. bike shorts over those. A balaclava thing for the neck, face, ears. Gore tex works well but isn’t truly needed, I find. Great if you see some at a thrift store.
If you pedal at a snappy rhythm in easy gears, you create less wind and go slower, but stay toasty warm from the effort. Most days I start unzipping layers if the wind goes down, and if I stop I stay warm quite a while. Your body is a furnace! Just don’t let the heat out.
Wind is enemy #1, but low visibility is #2. You don't see as well if you have stuff around your face. Drivers have foggy windshields, are messing with their heaters, and of course phones. And it's dark for longer. Be twice as alert!