For an ensemble that's pared-down but can be worn in a great deal of different ways, wear a white button down blouse and grey culottes. A pair of pumps instantly turns up the oomph factor of any ensemble.
White Button Down Blouse with Pumps Smart Casual Cold Weather Outfits
A white button down blouse and a charcoal tweed mini skirt are a nice combination worth having in your daily casual lineup. As for the shoes, you could stick to the classic route with a pair of pumps.