For plinking with a .22lr, I just picked up an airgun scope made by Daisy at Wally World for under $30. Ir's a 3-9X32, and it works just fine. And it came with mounts. For a few dollars more I could have gotten a BSA 3-9X40. However parallax with this scope would be set for centerfire ranges, more than is needed for rimfire.
If you can spend a bit more, a scope wit adjustable objective, and even target turrets, is real neat. On my bull barrel Ruger 10/22 I have a Simmons air rifle target scope of 6-18X40. Scopes like these
are avilable in more modest magnification ranges and even in straight 4X.
For your .22mag I'd go with a scope of at least 3-9 magnification of a centerfire type, as I imagine you will often be shooting at longer ranges with the mag. AO would be useful here as well. As would target turrets.
By the way, there's a company called Stoney Point that makes target knobs that fit on scopes with standard adjustments. They're available for Burris, Leupold, Tasco and Simmons.
You might want to look at the
http://www.natchezss.com/ web site. They have some demos and sale items you might want to check out, in particular a Simmons 2.5-10X50 for $49. In fact, many on-line dealer sites have clearance and/or closeout sections that offer some real good values.