After you hit Q to get into first gear, push joystick forward to start moving. If you hit Q once, then W you are just back into the neutral gear - no movement of course. There is a gear indicator at the drivers position.
If still nothing works, your stick may not mapped for Mode 2 yet (the standard mode for vehicles) - Just go to map controllers, select your stick, select Mode 2 and klick the "Copy Mode 1" button.
Two more tips:
- You can set your views in tanks just like in a plane. It's essential for the drivers position, where you can use the arrow / pg up keys to move your head outside the tank. Contrary to a frequent belief this doesn't make you more vulnerable.
- While moving, you can steer your tank from the commander's or gunner's position by using the rudder.