Minimum instrumentation for PPL training
If you can get another aircraft just to do the IMC and radio navigation flying element, then my list would be:
oil pressure
oil temperature
water temperature (if using a Rotax)
compass
slip indicator (ball, needle or wool tuft stuck to canopy)
altimeter
air speed indicator
In my view, the fewer distractions inside the cockpit the better. PPL training is all about looking outside and flying the correct attitude. I keep some round, white 'post-it' style items in my kneeboard, with which to cover up the non-essential instruments as required.
TOO
TOO