14/52 is pretty low, but 12/52 is the lowest. 19/47 is as high as you can go (recommended only with powerful engines).
Going smaller on the CB or larger with the spur will give a lower gear ratio. Going larger on the CB or smaller on the spur will give a higher ratio.
Unfortunately in recent years, in the sport of RC, certain experts have started to use the term 'high' and 'low' gearing incorrectly. This is causing all sorts of problems and they think they're being really clever because of it.
On a 2 speed Savage, geared 14/52, in second gear it has an overall gearing of 18.885:1. Compare that to 17/49 - 14.655:1.
18.885:1 is actually a 'lower' gear ratio than 14.655:1, even though the number 18.885 is higher than 14.655. Some people have decided to use the term 'higher' for the low ratios and 'lower' for the high ratios because of the numerical value aspect. Confused.com!!!
Just remember this - in a real car, you start off in first gear (the lowest gear) and work your way to 5th (the highest gear). Full-size Off road cars often have a 'reduction' box as well, this gives an additional set of lower gears (thus the term reduction ratio).