This is something I've actually spent some time on figuring out with my car. The easiest way to figure out: go to a dyno and do a run. From the torque graph and transmission gearing you can figure out at what speed and rpm to shift at. The goal is to keep as much torque transferred to the drive wheels throughout every shift. There is a lot of fine tuning to do, I find it a lot easier to do with an excel spreadsheet. Punch in a few formulas for the gearing, torque values and speed and you eventually have something to work with.
For example with my car, my optimal shift points are:
1-2nd shift - 7000rpm - 57.5km/h
2-3rd shift - 6900rpm - 95.5km/h
3-4th shift - 6700rpm - 138.5km/h
4-5th shift - 6400rpm - 178km/h
5-6th shift - 6500rpm - 224.5km/h (if I had a 6spd transmission)
Gearing matters, but only in the transmission, the final drive (differential) gear ratio and wheel circumference wouldn't change these shift points, just the speed they were made at.
It's different with every motor depending on torque and where the motor's power band is.
By the way, notice horsepower is never mentioned in how to figure out shift points and make your car accelerate faster? Because it's a useless number!!