Wow, super exciting - I'm looking forward to following your journey.
I'm around academics a lot, albeit in a more casual (west coast) part of North America. One thing I've noticed is that everyone starts out wearing their nicest, dressiest stuff in the fall and then slowly downslides into fleece, Gore-tex, rubber boots and yoga pants by the end of the year (profs included, although not so much with the yoga pants) as exhaustion, burnout, stress and rain set in. It's pretty funny to an outsider because it's so obvious.
At this university, students dress more casually than professors, and the stuff described in your OP would be dressy professor-wear. Dark jeans, tall boots, and a nice knit top would be dressy for a grad student here, in my DH's department. But I hear it's different (somewhat dressier) out east, and I know there are variations from department to department, too.