For a budget optic, I'd go with a Vortex Diamondback HP 4-16, I've had mine for a few years now and got it on sale at Midway for 200 bucks, far superior than the standard Diamondback. For a low, low budget rifle, my son's TC Compass Gen 1 6.5cm shoots amazingly well. I did the trigger myself and added a Ruger Hybrid brake, 5r rifled and Model 70 style safety. These might be too low of options but they definitely perform.