range, you want a tightbore throwing in it, get a new hop up rubber, make sure the compression is good and no air leaks, then find a nice spring - madbull/promethius/sytema, they give fantastic consistency (which is what you want to be accurate) and get everything on the gun set as you like it (I like my hop up set a touch high, to give a few extra meters range)
that should do your accuracy and range a nice boost.
ROF is fairly simple, get the battery size up from what you are using (an 8.4V would become a 9.6V) but don't go silly with battery size, most gearboxes can take a 9.6, but I would avoid going past 10.8V if you havent upgraded anything else (motor, gears, mosfet and things)