I recommend buying 50 extra controllers, maybe 100 if you're a controller breaker. Probably some ice cream to soothe your throat when you scream your head off in rage. And I'd say 25 tissue boxes for when something good happens and you cry tears of joy, or for when you just cry in general during Iron Banner. Also don't forget snacks and drinks, Doritos, Mountain Dew, and energy drinks so you don't need to rest.