I also work primarily from home but go out on “creative” meetings and teach classes, so I’ve been doing the same thing as Nicole. I chose to go the capsule wardrobe route, spending a bit more money on shoes and nice, high end denim and black jeans and a black blazer, and then mixing in lower cost (mostly Madewell sale items) tops into that equation. I NEVER wear skirts or dresses, so that makes slowly acquiring nicer sweaters and tops a bit easier.
My other big investment I’m going to make soon is a nice, professional winter coat. I read somewhere that your avatar in LA is your car, and in NY it’s your coat and bag. Currently, my avatar is a black bomber jacket with a gyro stain on the front then, I guess.