I second wool. For just cool weather (down to 32°F), I use thinner alpine ski socks. For down to about 25°, I try to find thicker ones. For really cold temperatures, I like over the knee cross country ski socks but those can be hard to find. About the only place I’ve been able to find them in the last 10 years or so is at
Cabela’s.
A couple more notes: Winter shoes that are waterproof and wind blocking will keep your feet warmer. Lake, 45NRTH, Shimano and even Sidi make them. They are somewhat expensive but are waterproof. You probably don’t need the warmest boot in those lines, however. You probably don’t need 45NRTH Wolfgars or Lake MXZ304s.
And you probably want to buy winter shoes that are a size or 2 larger than what you regularly wear. if you have thicker socks, regular shoes will be too tight and will make your feet colder.