In the picture above (me in the centre with RB gilet) I am wearing a Canterbury cold baselayer, DHB Runcton top, Endura RB gilet, Pearl Izumi cyclone gloves, endura thermolite skull cap, roubaix leggings, Endura waterproof shorts, RB endura bib shorts, merino socks & Endura thermolite socks. Specialized Defroster SPD boots.
The answer is layers and lots of them. You can always remove one if needed. The temperature on the day of the photo was below zero all day long.