I'll bike well below zero, and here's my usual gear.
Shell: flip between an Arc'teryx shell and a Marmot shell. I really need to get a better shell for biking as the Arc'teryx doesn't breath well enough and the Marmot isn't waterproof.
Shirts:
- wicking t-shirt
- Stoic long-sleeve 150 merino -- those two are enough down to 30
- thick Smartwool PhD 1/4-zip (bought a few winters back -- no link) -- add this when it dips into 20s and below
underwear:
Pants:
- Jeans or whatever
- Columbia storm pants -- whenever it's raining or once it gets snowing & the ground is slushy
Footwear:
Gloves:
Neck & face:
Helmet:- >33 = normal summer helmet
- <33 = Bern G2
Eyewear:
Light:
Niterider 550