What should I buy next?

I wouldn't bother with the hand held programmer if a supercharger is in the future, because you're going to need a different set up to tune the blower with later on anyway. Seeing as how forced induction is in the cards, you should buy components that are going to compliment it afterwards. Long-Tube Headers, High flow mid-pipe, larger throttle body, gearing…..not to mention depending on how much power you want to make, saving up to beef up the bottom end should be a priority as well. Don't waste money on the nickel and dime stuff, like CAI's, fancy spark plugs/wires, mufflers, etc, or anything that you’re going to have to swap out a second time later down the road.