For anything but super-precision shooting a PSA will work fine.

I'm also a huge fan of red-dot sights for people who don't want to spend 5 grand on ammo perfecting their shot. If you have a trigger pull that consistently makes you miss low and left, you can just adjust the dot to compensate instead of training for a better trigger pull. It's not what I'd recommend for someone to take up shooting as a hobby, but for quick results with less training and money (ammo adds up faster than the cost of the optic FAST), it's a good shortcut.

But go with a quality red dot like an Aimpoint or Holosun that won't require you to take 20 seconds getting the dot up and running if you need it. An aimpoint can run for a year+ turned on, so you just leave it on and change the battery on your birthday, whereas others like a holosun are motion-activated, so it automatically turns on when you pick up the gun and turns off after a few hours without movement. Same thing - change the battery once a year.

The cheaper bushnell, vortex, swampfox, etc optics are fun for the range, but you can easily leave them tuned on and have a dead battery in a week, or you may have to turn them on and set the brightness every time you pull the gun out, which takes time.

5.56 is plentiful and relatively cheap, though it does tend to be the first to disappear from shelves when there's a scare. From 2020-2022 it was hard to buy. It's also a little faster with higher penetrati9n than I'd like for indoor use. I like 300 blackout in a short-barreled rifle or AR pistol a lot for up close since it's less likely to kill the neighbor, and all you really need is a different barrel for it to work in an AR - it even uses the same mags. It's also amazing with a suppressor, as the cartidge was developed by a supressor company specifically to be supressed. But the ammo is also expensive and less-plentiful.