With regards to gear ratios and top speeds I have found they are disconnected with the real world of fighting robots.

Saint is not slow by any means and that works out (In theory) at about 9.25mph in fact is is probably closer to 8.25mph.

Gabriel is a little faster but probably only just into the 10mph in reality. These robots have very little problem with the arena surface so they can in practice reach these speeds.

Most people drive tin snail flippers. yes the wheels could with no resistance rotate to an expected speed of 15mph none has managed this in practice as they get stuck on the arena floor, experience roll resistance and other factors that slow them down, There are exceptions to this like Storm 2, and now Brutus. these are designed to use kinetic energy to knock and push there opponents into the arena barrier or pit. both are exceptionally expensive machines to build and run.

so remember in the robot scene as with most things in life

High speed costs!!! If you want a robot to be cheap and fun keep the speed down, the quality high, and the concept clever