You are only looking for home defense? You won’t be shooting at the range or competitions or using it for hunting/pest control?
The common answer is a shotgun. I’m personally more comfortable with a handgun. Especially in close quarters like a house. Most people disagree though. I take shotgun over rifle (don’t even own a rifle, semi or bolt or lever or pump) because of their shear all around usefulness. I would look into a 12 gauge pump myself. Mossberg 590 or Remington 870 are the big winners usually. Affordable, low maintenance, and reliable. I would look into safe or some kind of lockable storage to keep it in. You could easily spend more on storage than the gun if you are thinking shotgun.