I have a 3 peice grey/black herringbone wool suit from Zara that I love to mix up depending on the kind of job.
Jacket, pants, white blouse, black heels jacket, skirt, white blouse, black heels skirt, blouse (either white or a color), thin black sweathervest, black heels pants, blouse, sweatervest, heels skirt, black silk blouse, heels etc etc etc
I have made so many combos out of it, it was a great buy.