Weapons and gears from DLS obtained by game, but you will have to try. (complete all maps in a month)

[Robozvir]

Give players the opportunity to get things and weapons that can only be obtained for real money.

---- for example the Mosin rifle for completing all maps within a month. Better yet, give players the choice of prize they like.

I think this idea will serve as a great motivation to play again and again. Even if the player has everything, he will spend time helping a friend.