[Agent Minivann]

If you can get Rise of Valkyrie for anywhere near you're price range, do it. It is a better value than the Swarm of the Marro set. If that isn't an option, I would say to take some time looking through the units in the "Books" threads. Figure out what ones you are the most interested in that is currently available. You can only get a couple of small expansions. I would really recommend making that last purchase count as much as you can. If you find one that will get you the most bang for the buck (and it is common) get as many of that particular pack as you can.