Does a gyroscope require calibration? (MPU 6050)
Yes. It is always recommended to calibrate the MPU6050 or any other sensor before it is used for the first time as it might not have zero error. All you have to do is, place the sensor in a flat and level position and take the average of the few hundred readings. The gyro should ideally give 0 for all axes. There are many Arduino sketches available to measure the offset and use those as a reference. 

https://github.com/kkpoon/CalibrateMPU6050