Some useful guides
https://sectionhiker.com/winter-backpacking-gear-list-explained/https://sectionhiker.com/winter-backpacking-on-a-budget-gearing-up-without-breaking-the-bank/I did my first winter tour and experienced the worst weather I’ve been out in wearing thrift store clothes and cheap military surplus rain gear. Wore minimum of 3 layers and sometimes as many as 5. Slept in my summer bag, fall bag, a wool blanket and bivvy bag. The bivvy was useful as I was stuck inside a tent for more than 24 hours with two others and the condensation was awful, never seen rain inside a tent in the winter but rain it did. Snow kept filling the ventilation holes so we had to sleep with the door slightly unzipped, didn’t help much.
>pic related after the weather improved somewhat and visibility got better than 10m 