In a large mixing bowl, combine ground chicken, breadcrumbs, beaten egg, garlic powder, onion powder, salt, and pepper. Mix gently until just combined.

Roll the mixture into meatballs about 1 to 1.5 inches in diameter, yielding 12-16 meatballs. Set aside.

Heat a large skillet over medium heat, add olive oil, and cook meatballs for 4-5 minutes on each side until golden brown and internal temperature reaches 165°F (75°C). Alternatively, bake at 400°F (200°C) for 18-20 minutes.

Transfer cooked meatballs to a bowl, pour in buffalo sauce, and toss to coat evenly.

Slice buns open, fill with buffalo chicken meatballs, drizzle with dressing, and top with celery or lettuce.

Serve immediately or refrigerate leftovers in airtight containers for up to three days.