Go out and play with it a few times...figure out what you don't like and go from there.
The usual upgrades are a flow plug to replace the on/off (I would personally just make sure the on/off is not leaking and just don't use it), trigger, UL trigger frame or new chip and keep the original frame, clamping feedneck.
Don't bother getting a different bolt, the stock bolt is just fine. If you want better efficiency then go with an eigenring. It's your marker and your money, make it how you want it