Rode today when it was 0 / 32F and put down 20km... was packing a good deal of stuff too.
Was wearing a wicking t shirt, wool sweater, and a windproof shell, blue jeans (with no long underwear), and my light waterproof hikers with a pair of wool socks.
Had my toque and my wool flip mitts with a wool liner glove which works well in all temperatures and was carrying my nylon shell pants but did not need them.
For me it is all about the layers and although I live in a place where I can look forward to riding at -40 I do not use a winter jacket and do not change much on my upper body when it gets this cold save for switching to a merino base layer.
Will throw on the fleece underwear and use the shell pants, adding a base sock under wool socks and witch to warmer boots... I can use clipless shoes (with covers) down to 20-25F and these are weatherproofed and sealed to prevent water from shooting up through the bottom.
One thing I can buy here that might be hard to get are felt insoles for my shoes / boots... a winter shoe should be a little larger to allow for a thicker sock / insole and if you can;t wiggle your toes your shoes / boots are too tight.