For grilling- steaks, brats, or burgers. For low and slow ribs or the forgiving pork butt if you got time and mouths to feed. Anything cooked with your effort on a shiny new toy will automatically taste better. Make sure to report back.
My first charcoal cook as an independent adult was a small 8 rib rack of lamb, grilled indirect on a CGA. For my OTG first cook, I think I cooked some marinated tri tip from Trader Joes.