I have that exact IOR with a Dragunov reticle. I think it might be a bit much for his needs. It is one of the best AR optics imo, but will run around $400 after the cost of the optic and rings.
I had a leapers 6x. It came used on a rifle I bought. It broke rather quickly. Not a very good scope. But these can be bought for $25, so what do you expect?
A nice scope for a low price would be the Nikon Prostaff 4x. It's parallax set at 50 yards, so it will work well for up to 100 yard plinking. $99 at Walmart. Nice glass, lightweight. Does the job. IF $99 is too much, I'd then recommend the Bushnell budget scopes. They are better than BSA or Simmons in my opinion. You can get a 3-9 for $50-$60 and it should hold up real well on an AR-15. Some of these have adjustable objectives.
For $125, you could pick up a reddot like those made by Ultradot. Lifetime warranty on these. I believe they come with rings too. Simmons, BSA and the $40-$70 dots don't seem to be bright enough for daytime use. Stay clear of the cheap ones.
There really isn't a whole lot good options in the budget range. However, it should all work fine for simple range blasting thanks to the AR's no-recoil. Out of all these choices, the Nikon is by far the best as far as optical quality. I'd look through one before I'd decide. The Nikon is probably the least expensive scope that is treated like an expensive scope in its construction, waterproofing, lense quality etc...
If you bump up to the $200 range, your options grow immensely. Brands like Bushnell's 3200, Burris and others come into play. $300 range starts to give you options for military-style optics.