how a motor should be geared?????
I know alot of people will disagree with this, but here goes anyways.
Try to find one or more people who are running the same Motor as you are. Find out what Final Drive Ratio that they are running
Spur~Pinion X Transmission ratio = FDR. This will give you a ballpark idea of what to run on your car. From there your on your own.
As everyone else has pointed out, without the Same Car, same Driver, track, Motor, etc, etc. It is impossible to give a more specific recommendation as there are just too many variables to account for.