It's all about layering and avoiding synthetics. PLUS, get dressed where it is cool and don't go in and out of a heated building. Sweat is your BIGGEST enemy!
I start with stripping all of the way down. Wear loose underwear to trap your own warm air right next to your body. I like to wear long underwear pants and then put on sweat pants. Most of the winter these keep me warm enough. Make sure that you wear something like a long sleeved, cotton t shirt as your first shirt layer.
You will NEED some wool. Most stores sell woold socks. If the tag says "WOOL-85%, NYLON-15%" this works well bc the Nylon is the elastic to keep the socks up.
If you are small, check our Army Surplus stores. Most of the larger surplus wool sweaters are pretty much gone, at least where I live, but using one of these are your second layer over the t shirt keep you VERY warm. I would top this with an oversized sweatshirt.
Buy A gator. Here are some possibilities: Winter Cozy Helmet Cover - Statelinetack.com First Lite Merino Wool Lightweight Neck Gator by First Lite for $35.00 | Diggs Outdoors
BUY EVERYTHING BIGGER THAN YOUR NEED!! You won't be warm if the clothes are tight.
Buy an oversized vest. I'm about to convert a very old and holey green army blanket into a vest, now that I've cleaned my house for the holiday and gotten my wintering for my animals about done. Buy one in the men's department and get one with inside and outside pockets so you won't lose your keys of phone in the snow. =b
I do my winter chores almost exclusively in old sneakers. Only when the snow is deep do I put on boots. You will have wasted your money on nice riding boots if you wear them do muck stalls bc they are the warmest shoes that you own.
ALSO, accumulate as many wool and cotten socks together where you change to got outside and do your chores. Find a place to hang them to dry bc if you wash them every time you wear them they will only last 1/2 of the time that mine do.
If you drive to take care of your horse, bring a bag with your outside clothes and completely strip and change your clothes at the barn, and then change back to your driving clothes when it's time to read. COVER YOUR HEAD and cover your hands.
If you layer right, you will be very warm and will probably have to take off a top layer once in awhile to be comfortable. =D