A Cessna 172 pilot reported a complete electrical system failure; which necessitated a diversion to a suitable airport using only basic instrumentation.

Narrative

At approximately XB:00EST on a flight from ZZZ to ZZZ1 with VFR flight following from ZZZ Center; while approaching the cruise altitude of 8;500AGL; the fuel gauge for both the right and left fuel tanks indicated less than half full. The reading of the fuel gauges indicated incorrectly because both tanks were topped off before leaving ZZZ at XA:30. Shortly after noticing the false fuel gauge readings; the electronic oil temp and pressure gauge displayed green; orange; yellow; and red before settling on red. The Garmin GPS screen also cut off and radio communications were flickering in and out not allowing transmission to gain assistance from ATC. In an effort to gain electrical power; I cycled through the Alternator Failure checklist; however; there were no low voltage indications or popped circuit breakers. After completion of the checklist; comms were completely gone; and so was the transponder- unable to squawk loss of communication. As I was unable to restore electrical power to the airplane at 8500ft AGL; with the use of my Magnetic Compass; Airspeed Indicator; attitude Indicator; and Tachometer; I maintained altitude and a safe airspeed to turn to an easterly heading to help determine our position and the nearest airport. Still having engine power; it was determined that ZZZ2 would be the best option for a safe landing. In the interest of safety; I directed my passenger; also a private pilot; to contact the ZZZ2 tower via cell phone while I navigated the airplane to the airfield. About five miles from the airport; we received light gun signals and cleared to land on RUNWAY XX and taxi to the FBO.