If I were taking out someone with zero experience with firearms, I would not start them out with a 12 ga shotgun. There's several good reasons, not the least of which is the recoil and risk of developing bad habits related to the recoil. I'd start them with a .22 caliber rifle, either a bolt action or lever action. If you don't have either of those, a .22 semi-auto would be next. If all you have is a shotgun, I'd limit him to low brass bird shot. It's always better to introduce a beginner to the sport with something not painful or intimidating. As to specialty ammo... Very expensive, assuming you can find any these days. Ammo of any kind is currently scarce. You may find #8, #8 1/2 and #9 shot. This stuff is much less expensive.