Well, what do you have already?
I've got 3 postban AR15s and an AR10, I'd either get another custom AR15 upper as well as a custom AR10 upper or I'd look to further expand my collection.
Since I've already got an AR10 and own a couple AR10 mags that came from the legal Armalite AR10/M14 magazine conversion kits, I could buy an M1A and already have magazines for it.
If I wasn't stuck in Commiefornia then I might look into getting a preban AR15.
Since I AM stuck in Commiefornia, most of my future plans revolve around custom AR uppers, accesories, or long range bolt actions.