Hmm- well, I'm hardly new to firearms. I grew up with shotguns, .22s, & later, deer rifles. Formal instruction was from NRA, Scouts, & former LE instructors, even one former Army range instructor.
No argument on the safety ideal- all guns are always loaded, don't point it at anything you aren't willing to destroy. Still, I stand by the idea that in *Practice*, it's easier to get 'em to actually doing that, then *living* that, with a long gun.
I own a very serious handgun, plus a smaller yet pretty serious handgun that's much easier to conceal. But if trouble comes at home, I'm grabbin' the shotgun. Much of what's said about training & practice boils down to building familiarity & muscle memory- under stress you do what you have long experience doing- and for me, that's a pump gun with safety on the trigger guard.
A handgun's advantage is portability. For concealed carry, or to take along in the car, it has no peer. But at home a shotgun has some advantages too. Example- with a pump, there's nothing like the sound of racking the slide & chambering a round to make someone decide he has urgent business elsewhere.
And the way our little town is going, it could happen here any time.
So to the OP I'd say, a good DA .357 revolver, as dkryan described above, is surely the premier home defense *handgun* for the first-time owner, you betcha.
Still- you might try a few shots of light-load birdshot in a 12-ga riot gun, then maybe work up to a round or two of buckshot. You might decide to make that your 2nd gun.