This is what I have but not installed yet being lazy.

AIR/fuel meter (just for looks)
Oil Pressure
Oil temp
Boost guage


Exhaust temp( have not bought it yet but Randoms recommendation.)

Is there really a need for voltage meter?

 

A vacuum gauge is pretty useless unless you somehow think you're combatting a vacuum leak... In which case, the best tool is an aerosol can full of ignitor fluid, not a gauge.