I like my Diamondback scope a lot & optically they are about equal to the Leupold gold ring, as far as I can tell. But then my eyesight stinks.
I also own a late-model Tasco, a Simmons, and a Redfield, they all cost around $50, and I would consider them only if you are so desperate this is all you could afford until you can save up the money for a good scope.
This is a shame because I have Tasco scope and Redfield Scope from the sixties and they are very good solid models, if not up to all the modern advancements.