Layer 1: Wool base layer (cheap @ Target).
Layer(s) 2.x: Whatever.
Layer 3: Windproof shell (no insulation.)
If you can ride a bike in a down jacket and not get drenched in sweat, you're not riding hard enough.
Yesterday morning it was 18 degrees. I wore; t-shirt, long sleeve shirt, another heavier t-shirt, button down denim shirt, 2 zip up sweatshirt jackets. Bottom half; pajama pants, jeans, 2 pairs of socks, gym shoes. Winter atire; hat, backlava, lobster gloves. My toes got very cold and I am trying to find a solution for cold toes.