Probably the most beneficial would be a barrel/barrel set, and an on/off. After that you can start looking at other things like bolts, QEV and a board. The stock Ion board is probably fine for you,unless you really want several different types of ramping, breakout modes and other things but if you see a good deal going on one, nothing to stop you Probably gain more experience with the stock board anyway, seeing as you actually have to do something to make it shoot at a reasonable ROF