Don't leave loafers for the boys: there are plenty of sleek styles that feel professional. Choose a shoe with a pointed toe, and you'll let everyone know you mean business. Nicholas Kirkwood Two-Tone Polished Leather Penny Loafers ($300, originally.
This look is both casual and lady like at the same time. I have a black skirt that's very similar to this and nude pumps of course. That grey T is something I would have to acquire though :)