I am not an explicit expert, but moat AR platform guns will serve you well. Some feel cheaper than others, but anyone you can get your hands on at this point, if you can even get ammo is better than none. That out of the way, if you can be picky on ANY aspect, make sure you have an AR that can shoot 5.56. It will say this somewhere on the gun. 5.56 and 223 are extremely common ammos and both can go through the gun. If it's rated for 5.56 you can use either ammo. If it's 223, DO NOT USE 5.56 IN IT. It will eventually cause a catastrophic failure, in your face. Everything else is nit picky. Optics are to taste, rail systems as well, iron sights are good for practical defense applications.
I am not an explicit expert, but moat AR platform guns will serve you well. Some feel cheaper than others, but anyone you can get your hands on at this point, if you can even get ammo is better than none. That out of the way, if you can be picky on ANY aspect, make sure you have an AR that can shoot 5.56. It will say this somewhere on the gun. 5.56 and 223 are extremely common ammos and both can go through the gun. If it's rated for 5.56 you can use either ammo. If it's 223, DO NOT USE 5.56 IN IT. It will eventually cause a catastrophic failure, in your face. Everything else is nit picky. Optics are to taste, rail systems as well, iron sights are good for practical defense applications.