I’m a cheap person, and you don’t need a great coat. I’m wearing a somewhat worn 15 year old coat at this point that’s lost a bit of it’s insulation. No single item will keep you warm. You need layers.

Get a wool base layer like for skiing. A good hat, scarf, gloves. You can get a thinner pair of gloves for under your winter gloves if you get cold. A balaclava or skiing face mask. And, a decent coat. If it gets real cold you can get some ski pants to wear over your base layer and regular pants.

That being said, you’ll also want to keep agility in mind for the climate wars.