Your thread title here said "First firearm". Is this the first firearm you've ever shot, or just the first you've ever owned? My point being, if you've never shot a gun before, be prepared for a 12 gauge shotgun to step you back a bit! Stay away from 3-1/2" and magnum or buckshot or slug loads when you first shoot. Get 2-3/4" shells, light loads possibly, filled with small birdshot. Keep the buttstock firm against your shoulder and lean forward into it.

I would have probably sworn off guns from the very beginning if the first time I ever pulled a trigger was on a 12 gauge. I'm not trying to frighten you off. With just a little time, you won't find a shotgun or high powered rifle bad. But that first shot with a 12 gauge, if you don't really know what you're doing and how to hold it, will hit you like a car's airbag.

If you are a new shooter, you might want to find a friend who will take you shooting with something a little gentler and train your a bit on your first time out.