Keep it simple, keep the cost in line with the value of the gun.
A pretty decent scope is the Simmons "22 mag" line, with variable power (3-9x) and a 32mm objective. With rings, it'll run you around $50. I've got a pair of these on 10/22s and for everyday use, they're perfectly adequate. Price-wise you can go up or down, but this one is a good compromise. I got mine from Optics Planet, who also offers some good introductory info about choosing and using a scope here: How to Choose a Rifle Scope - Riflescope Experts Guide to Firearm Optics - Rifle Scope Selection Tips