I have a S&W M&P Sport II, It has a decent trigger and has gone bang every time I have pulled that trigger. No feed or jamming issues. It hits where I aim it. The basic rifle is a good rifle, the furniture is the most basic stuff available, probably because the first thing people do, is replace the plastic parts with stuff they like better.
As sold, the M&P Sport II is a completely functional rifle, melonited (or whatever S&W calls it) barrel, flip up rear sight, and a decent trigger out of the box. I have rifles with optics on them, so I put a carry handle rear sight on the M&P and have a great time with it.
I have had good luck with my PSA purchases, others have nothing good to say about PSA, but I have no complaints with fit, finish, quality, accuracy, reliability, or price.
A basic 5.56 AR with as much ammo as you can find/afford will probably serve you well. Shoot it and figure out how much Gucci stuff you just have to have, or maybe just the basic rifle will be fine.
Good luck.
When I say hits where I aim, the rifles are more accurate than I am, with the ammo I have. I do not fancy myself as some gold medal competition shooter, far from it. But I do have fun !