I bought a Barska 3-9x 42mm IR scope for a decent price on Amazon. I really like it. Attaches directly to picatinny rail and sits very solid. You can install a battery to activate the illuminated crosshairs. It lights up either red or green with 5 intensity options for each color. Without battery, crosshairs are black and work really well. Had it dialed in quickly and easily and its been a great little optic since. I highly recommend.
Heres the link to the scope on Amazon which is the cheapest I've seen lately. Good luck!
A lot depends on your intended use.......... but for "funnin and gunnin"
I like ........ Weaver 1-3x20 for a scope ( $180ish)
Red dot........ A Bushnell TRS-25 with a riser.....( $100ish)
I've still got a old Bushnell Trophy 1X32 red dot on mine....looks a bit like an ACOG.......... my 15-22 is a fun/trainer range gun..... mostly out to 50yds.....
Among the most popular budget red dots is the Bushnell TRS-25 and Primary Arms MicroDot. Both under $100. See Primary Arms for both optics and needed risers too. Sometimes Palmetto sells the Bushnell TRS-25 for pretty cheap on sale. Just have to catch it when they do.
I've had the Primary Arms MicroDot for several years.
I have a TRS-25 too. I think it's a good match for the 15-22. It's light, inexpensive and it works. I got mine for around 65 bucks on sale and used a UTG riser for co-witness. I have heard that they changed the design of them slightly though and some folks aren't happy with it. Seems they moved the emitter from the 4 o'clock position to the 6 o'clock and it's more intrusive to the field of view. They say the dot disappears in the top 1/3 or 1/4 of the field of view too. I have the original style and I really like it.
I have a Bushnell Shotgun scope that is a Dawn to Dusk 1.75x4x40mm on my 15-22 and it is perfect for it. I zero at 50 yards and I just blow out the bullseye at 50 yards which is great for a plinker 22.
So pretty much anything for an ar would be ok? Looking at the trs-25, but not real sure. Maybe a trs-32. How far out is a red dot good to. This will be my first red dot. Do I need a riser for any Red dot I put on and is there a size that would be best. Thanks