It's not magnetic compass, turn coordinator, stopwatch, wind meter, VVI, and airspeed indicator. I want to know what is the first flight instrument.
The Wright Flyer, arguably the first controllable aircraft, had three instruments:
A stopwatch to measure air time.
A crude tachometer to gauge engine speed
And an anemometer, to make an estimate of distance traveled by measuring airflow.
I believe the correct answer (and the answer that you looking for) would be the forerunner of the of an artificial horizon, the yaw string. The tendency of airplanes (particularly pioneer aircraft) to roll needed to correct in a timely manner, and the visual earth horizon reference was not an effective means of detecting slip or skid in the necessary timely manner. Consisting of a suspended short piece string or yarn, often weighted the bottom give the pilot a quick measure of the side slip angle of the craft.
However, the magnetic compass in my opinion would be the first true instrument. Of the seven standard flight instruments, the altimeter, attitude indicator (artificial horizon), airspeed indicator, magnetic compass, heading indicator, turn and band indicator, and vertical speed indicator, the magnetic compass was not only an existing instrument, but would have become a natural necessity as flying evolved from the day-light, good weather over ground with recognizable landmarks, to night time, over water or monotonous terrain, or limited visibility, etc.
Early flight in conditions that disallowed landmark and horizon earth reference often used dead reckoning as a means of navigation. The ability to maintain a constant and correct direction of travel is essential to dead reckoning. A magnetic compass would have been the logical first step.
However, the earth magnetic fluctuations, mistaken speed of travel, and travel heading deviation (the sidewards travel of a vessel as the result of forces (such as wind, currents, etc.) makes dead reckoning as means navigation by any means of transportation, well, dicey. Consider 50 mile due south flight over water with no visual references, if a easterly cross wind deviates the flight path one half mile laterally for every ten miles of flights, then, even with a correct speed in relation to ground, the pilot could of the mark by two and half miles. Thus many other flight instruments had to be developed to bring aviation to where it's at today.
Known as Gyro, Lawrence B. Sperry, a well known for many innovative flight instruments he constantly conceived, developed and personally tested. Gyro was one the first to fly at night, regularly army night flights in 1916. Todays modern aircraft still equipped with the basic flight instruments the Sperry developed.