My suggestion is to study the Mix & Match Quilt Block Collection brochure that AccuQuilt has on their site. That particular document really helped me determine which dies I could not do without. Also, the BOBs are really nice to add to your collection.
Also, keep in mind, some dies can be used to make additional geometric cuts; the strip dies can cross-cut for the same size squares; ex: 3 1/2" strip cross-cut to 3 1/2" squares, etc.
You will love the AccuQuilt cutter and I agree with the other member that thought she would only need a few select dies - you will end up buying "all" the dies!