Wool socks work great for me.. just make sure they aren't too tight, that really reduces their effectiveness.
I use
these rain covers with merino wool socks and they are good for me up to -5c or so. After that I think it's a loosing battle until you get a winter shoe/boot.
Make sure your legs/ankles are warm also as that directly impacts on your foot temp.
Gloves are hard for me because I have lots of open finger cycling gloves and lots of winter gloves which are good around freezing and lower. Something like
this would probably bridge that gap.