Current limit should be set based on the motor specs. If you set it too high above the motors rated current, a stall can permanently damage the motor, by de-magnetizing it.
Best way to set gain and damping is to start with both at a low-ish level (Gecko recommends starting at 10 or 11 o'clock position - about 30% of full scale, then gradually increasing gain to make the servo "stiffer", and adjusting damping to eliminating ringing and overshoot, while maintaining "crisp" response. Keep in mind, none of these settings have much effect on accuracy, unless really massively mis-adjusted. What they do is make the servo respond more quickly, allowing you to achieve higher rapid speeds, with higher accelerations. With G320s, it seems best to adjusting damping so the servo "chirps" about once per second when the motor is not moving. For G320X, adjust so it is silent, with perhaps a soft chirp every few seconds.
Regards,
Ray L.