Fleece lined leggings. They will keep you warm and are just as comfortable as sweats but, when worm right, look much nicer.
Nice gloves will last you a long time, even if you gain or lose weight. You gotta keep your hands warm, might as well do it in style.
A nice coat. I'd say a trench coat or pea coat in a neutral color. You can put it on over jeans or leggings and immediately look more dressy and presentable.
A good pair of boots. Whether you prefer a small heel or a riding boot, again, they make you look pulled together and will protect your feet from snow and slush. Make sure they're comfy.