Up until this past summer, I never had to dress in business professional. Every single one of my past jobs was always business casual or extremely casual. There wasn’t much of a difference to me up until recently when I had to start dressing business professional all the time, even business casual had to be done up more than I thought.
Think solid neutral jacket that matches solid neutral pants, knee-length skirts, or dresses. If pants and skirt, then pair with a nice blouse. Add an appropriate height heel, closed toe also in a neutral color. I personally would take a bag in a neutral-ish color (or in red, green, or blue) to add a bit of personality in my outfit while still keeping it professional. I would also keep the jewelry to a minimum with dainty pieces or simple studs.
Business casual is a little more open to interpretation. Dresses, skirts, and pants can have more color or a simple pattern. Jackets may be optional and don’t have to match. Still keep a more neutral closed-toe heel and bag. Depending on the outfit one could add a piece of statement jewelry or keep it dainty. I typically wear a nice skirt with maybe a slightly more casual top or a blouse (my turtle necks may or may not have been making the occasional appearance.
As weird as it may sound, I love shopping for suits and work clothing pieces. I think they can be a great way of showing off a bit of your personality while still keeping it professional! A great place to look for some inexpensive pieces is H&M as well as the Ann Taylor or Loft stores. I always raid their clearance and sale racks for any great discounted finds.