I'm assuming a mini gs?
If that's the case, I wouldn't upgrade the on/off, that would be a giant waste of money. Barrel, for sure, I love the SP freak kit. I don't mind the stock trigger at all now that I was able to pick up the last trigger pin from Boss (I think they need to produce some more again, it took all the side-side play out of my trigger). Bolts=meh, depends on how much tinkering you wanna do with your gun, nothing is worth buying except either the boss bolt or lurker bolt, otherwise don't upgrade. IF you do buy one of those its not just a simple drop it in (at least the lurker) and go, you have to find the right configuration for it to work right and well.