Black blazer (or even a full black suit) - I found one at Zara the other day that I think I will go back for. You can't beat the price!
Black flats. I have a pair of Cole Haan ones that have been worn out and are no longer suitable for the office so I need to upgrade them. I like this basic style by Cole, but also this pair from Michael Kors.
Wrap dress, probably in black. (I realize that this summer wardrobe is oddly dark, but so far these things are good staples). The Gap has a simple style but I think it would be too long on me.
Colourful blouse (or two).
If I go shopping with what I want in mind, rather than just looking at anything, then I am usually more successful so we'll see what I can find, without spending too much money.