Board Thread:Questions and Answers/@comment-12.111.134.2-20121228160752/@comment-5149596-20121230092615

Spinners are devices that a player uses in order to play the Ninjago Spinjitzu Spinners game. A LEGO Minifigure needs to stand on a Spinner in order to fight its opponent properly, spinning around and attacking with whatever weapon it may wield.

Sounds to me like you're in need of the 9579 Starter Set! I say it would be perfect for your son if he doesn't already own it, because it comes with two Minifigures, two Spinners, ten Cards, six weapons, and an arena! Though if another Spinner set isn't what you're looking for, then I would recommend the 9445 Fangpyre Truck Ambush. It comes with four Minifigures, four weapons, and two vehicles! :D