A 3-9x40 is the classic hunting scope choice, and would work fine for target shooting. For hunting, you want the best glass you can afford, for making those low light shots. You definitely want to get out of Chinese glass. I'd say the minimum you should aim for would be the Leupold Rifleman/Redfield Revenge/Vortex Diamondback/Burris Fullfield II/Nikon Prostaff level of optic, all of which are roughly equal in optical quality and are in the $150-200 range new. If you have a higher price range than that, tell us and we can make some more recommendations. The roles you are describing don't require any fancy reticles, turrets, or any of that, so get a scope with a plain duplex reticle and capped turrets, and spend your money on glass quality and build quality.
Whatever you get, you will want a good one piece mount or extended riser+rings setup that gets the optic far enough forward for good eye relief, so remember to budget for that too. The ghost of Eugene Stoner casts a cute little puppy into the fiery pit of hell every time an AR noob mounts a scope directly to the receiver with rings.