New players should focus on Arrow keys for movement, Z and X for Turrent, Tab for scors, and Plus/ Minus for Viewport size.
As you collect items for later usage note that you use them by pressing the numbers (1 to 5)
Few other notes:
Tanki Online 2.0 is still 100% free. You can buy upgrades for real money and that way you support and help the development of the game.