Hi Miguel,
What do you mean as accuracy?
Generally gyroscopes have got several accuracy errors.
First is the zero-rate level. It usually drifts a bit over time and with temperature.
Second is the sensitivity which changes over time, temperature and might be influenced by acceleration.
Third is the non-linearity of measurements
Fourth is the aligment of sensor.
Then come all the errors connected to ADC processing.
And once you start to add the measurements to get the angle of rotation over time you start to add the drift error over time - which grows very fast.
That's why you need other sources that measure angles of rotation (but are way slower then gyroscopes). A mix of accelerometer (measuring earth gravity vector) and compass (magnetic vector) is used usually.
This way using some filtering (Kalman filter used usually) you make sensor fusion and at the same time minimalize drift by calculating proper zero-rate leven and sensitivity over time.
Hope it helps