Most of the best upgrades are free or just cost you some materials. If it's a mechanical trigger then polishing the tip of the sear that catches the lip of the hammer and also polishing that lip will go a long way to reducing the trigger pull effort and make the pull smoother. Drilling and installing a setscrew as a trigger travel stop will all but eliminate the post firing trigger travel that is part of the regular trigger. That makes the trigger travel a LOT shorter and makes it easier to fire faster.
With your $30 I'd invest in a delrin Boss bolt. The lighter delrin bolt reduces the kick by quite a bit. It won't make it super smooth but it makes it nicer while still retaining a bit of kick to let you know you're shooting something worthwhile...
But if you're not planning on keeping your R6 for a long time then I'd save your money for the next marker.
Frankly I love my own R6. It's been upgraded with my own made delrin bolt and I use a Lapco barrel on it. As part of the delrin bolt mod I made it so it accepts the flush cocking back pin so it's not hitting me in the mask. The thing shoots sweet and consistent with decent paint and the remaining kick is enough to let me use a gravity feed Archon hopper and have zero chops regardless of how fast I pull the trigger.
My next mod is to use it with a red dot sight so my first shots are already zeroed in on target as best as possible. It won't guarantee a hit since paintballs are not that precise but it at least my chosen target in the center of the circle of probability of a hit.