It really doesn't need anything out of the box unlike all the other mini 4WD cars out there. Maybe a tiny spur and a giant pinion if you're running 21.5 or 17.5 due to the ridiculously high internal ratio. (2:1)
I too picked up a used Genetic but then decided to not build it up since i would sink another $150 into it after it was all said and done.
There are guys at my track who have been running it box stock and have been doing fantastic with it. Some of the aussie guys have broken the stock steering arm on the center post but thats about it. The hardware is all metric and seems of much higher quality that the ones that came on the original Photon, which stripped easily.
Dan, what are you using for diff oils, motor (17.5, 21.5), spur that comes with kit is 84. I thought about starting at 100 spur 25-30 pinion for 17.5.