I agree with all the posters who say wool, layers, and heated items. I live in the Canadian prairies and it gets cold. Last week, with wind chill, we hit -55c which is -67f. It’s not always that cold (this morning it’s -14c which is downright balmy) but it is routinely -30c or colder throughout the winter.
I always wear wool socks. I typically wear blundstones but on really cold days I will switch to my kamik winter boots. I will wear fleece lined riding tights, and when I’m not mounted I will wear fleece lined carhartt pants over top.
I wear the most layers on top to keep my core warm. Typically I will wear either a wool long sleeve shirt or a tmax heat shirt. Over that I will wear a down vest or a heated vest. Over that is always a down filled winter jacket that goes past my hips. I will take this off to ride. On VERY cold days I’ll also put on a sweater between the vest and the jacket.
For my hands I will always wear fleece lined gloves. Sometimes I wear my heated gloves under them, but the battery pack is a bit bulky so I save that for extra cold days. I will also put fleece lined wool mittens over top if I need the additional layer. When my hands get too cold I lose all dexterity.
Finally I wear a fleece lined neck warmer that goes down to my chest and up over my ears/nose. Sometimes I’ll put a scarf over top of that. And I always wear a toque. Sometimes I’ll take off the toque in the barn to groom, sometimes it stays on.
For me the brands of things don’t matter as much as the material they are made from. Wool, fleece, down… these are my go-tos. I know lots of people also swear by silk but I haven’t added that to my wardrobe so I cannot comment.