It depends on what kind of ECU you are running. I would say water temp, fuel pressure and widebands are important ones to have if you have OEM ecu. If you have a stand-alone you can have fail-safes built into each thing. Good example is if my AFRs start to lean out when In boost the ecu will resort to waste gate pressure. Gauges also become useless when in boost, you simply can not watch everything since priority should be the road at which you’re doing a pull on..
Since I’ve gone standalone I’ve slowly started to eliminate gauges. I may also be getting older lol