My app is a 5 starts app, it never moves in the stupid rank (always around 300) cause I refuse to pay 5K-10K to scammers that put a tiny icon in their f* ads network.
I advertised with AppGratis for free in 3 occasions, got almost a million downloads total and many more 5 starts reviews..first overall place in many countries, fourth in my category in USA..that saved my app, three months after last time still feeling the effect (but also as now back to the invisible part of the rank)