I agree with Alvin about wind blocking being important. I know I’m a little late to the party here, but I’d like to offer up my strategy for staying warm…. (First should be noted, I ride in Texas, and I usually don’t ride below 35 degrees)
1. If Its not a ride that needs knee pads, I really like insulated lycra biking pants. There might be a better name/term for them, but I basically went to the bike shop and that’s what I asked for. Anyway, keeps your legs warm through almost anything, but problematic if you wanna wear pads. If its not super cold, just wear normal biking pants and knee pads, and that will block most of the cold air from your legs.
2. I like to wear a hoodie, obviously the colder it is the thicker the hoodie, with maybe an underarmor long sleeve shirt (like a rash guard), or some kind of moisture wicking shirt underneath. This combo serves me well for keeping me warm once the riding starts and my blood gets flowing.
3. The rest is just obvious little things, full finger gloves, and cycling shoes that are insulated and water resistant. Full face helmet can help keep your face warm too 😉
IMO, the really cold days are the best time to tackle the most physically demanding rides. You don’t have to worry about overheating, and if you dress right you can essentially recycle your own body heat.