If you don’t have an AR get one. Several great choices.
For single shot long rifle: .308 Rem 700.
Shotgun: Rem 870
Both super reliable and the 700 you probably won’t find a more accurate long rifle off a production factory floor.
Couldn't possibly agree more on the Remington 870 recommendation, adding only to buy the express version which can be modified to hold additional rounds. If one shops around, it's fairly easy to find the 870 for under $300 and used re-loading kits are also easy to find.
Just sayin' ...
BTW: in addition to the 870 for home defense, a good .45 or 9mm for close quarters is also in order. I prefer HnK handguns over everything else, but that's personal taste. I have large hands, need the large grips of the HnK's.