I'd buy the largest caliber, that all the people who will be using the firearm, can shoot well. AT least a 9mm, but preferably a .357, .40 S&W or .45 acp. Check out a shooting range that rents guns and see what works for you. My primary home defense/carry pistol is a Sig Sauer P229 in .40 S&W. Revolvers make an excellent choice for novice shooters (and experienced shooters, too) because they are easy to operate (just point and click). Regardless of what you choose, seek proper training. Not only on how to shoot, but when & when not to shoot.