Marciokoko:
So with an Arduino and 4 motors and 4 mosfets I should be able to do something that might at least lift up and hover for a few minutes and maybe turn a bit and land, without hurting anyone. Oh and a gyro and axlrometer.
Not quite that easy. You will also need a battery, and a frame on which to mount everything. And some wires and discrete components (resistors, mostly).
A gyroscope and accelerometer will allow the flight controller to stabilize flight but won't allow you to maintain altitude or position or avoid obstacles. Using just those two is sort of like walking around with your eyes closed and your ears covered. Your inner ear will still tell you which way is up and if you start moving or turning but not what direction you are facing, how fast you are going, or what floor your elevator is at. You can add more senses (barometer for relative altitude, magnetic compass for absolute orientation) but for a simple flight controller you would typically hook up a radio control and put a human in the control loop. The human provides the senses and feedback to hover and fly around obstacles (with practice).