Please show us your test code and verify you are giving it time to calibrate before moving.
And:
Gyroscope Filtering Discussion - #18 by Electrobotz
Another question, How do I properly use the Gyro sensor
https://renegaderobotics.org/getting-started-with-the-vex-gyro-sensor/
http://www.robotc.net/blog/2011/10/13/programming-the-vex-gyro-in-robotc/
PROS Gyro Integrator
Gyro Acting Weird (V5)