Climbing Solo Top-Rope

Hi everybody I have some doubts, hope someone can clarify it for me. I go alone to train to a climbing gym near my house, it has boulder and routes areas, but it is most of the time empty (in the mornings, when i ussually go), so I can not climb routes with anybody. The static ropes are already set in the routes, and I know that it is possible to do solo top roping, but I don´t know what it is the best device to secure myself, so before I buy one I would like to know your opinions. What´s the best one? I mean: -What is the cheapest? -What is the safest? -What is best for auto-feeding the rope? (I have gri-gri but I hate having to feed the rope my self) -What is the easiest to set up? -What's less harmfull to the rope? I was thinking about petzl croll, but i dont know if it feeds ok the rope, and i thinks it harms the rope, doesn't it?... Thanks everyone in advanced for your answer. Sorry for my mystakes in english, I'm not native ;-) Climb on!