For daily login and playing 80 games you can get much rewards. How much you obtain it will depend from you: only free, or part level you are able to play or completely season that all you can get in Rollercoin.
You can do easy 35 level, rest you have to buy
Event has lot of reward, which you grab?
It depend, when you started and how hard you play so much levels you are able to get, good luck
Best time, when buy standard pass (or full) is day-two before finishing season. In the time you will know, if you really want it. Good luck!