I'm on my bike for 4-8 hours a day during the (lower) Midwest winter, so I can probably offer some advice. The hardest things to keep warm are hands, feet, and to some extent face. Core is important but if you have a good jacket or two and maybe some base layers, you should be fine. Legs are whatever.
For hand coverage, I wear light winter gloves or even work gloves for any temp over freezing. For <25-30, I just use these Celtek lobsterclaw snowboard mittens. Anything warmer and my hands start to sweat uncomfortably, the mittens are THAT warm.
For the head, usually just a normal wool cap. I don't usually feel like I need face protection unless it's <25F, in which case a neoprene balaclava is great. If your eyes get really fucked up by the cold, you can get some snowboard googles, too. edit-- I also generally pack some basic shop glasses if it's going to rain or sleet, because squinting through that shit sucks, but I also don't care enough to pay for real ''cycling eyewear.''
For foot coverage, I switch to less ventilated shoes (right now, Chrome Kursk Pros), and neoprene booties over those if it's <25F, or cold and wet.
For the core, any combination of these, depending on temp/conditions:
-Merino wool or synthetic jersey base.
-Pearl Izumi soft shell for most days, hoodie under that if it's <35F.
-Slightly heavier, but still light Marmot shell if it's <25F, hoodie under that if it's even colder.
For legs, usually just merino leggings and regular-ass work shorts or pants over that, depending on the temperature.
tl;dr-- Marmot and Pearl Izumi make good shells and snowboarding gloves work well. Get a balaclava if your face is cold.