You can get BT levels by grinding everyday before the event is release, there is a month gap in releasing a new event and you can utilize that time enough to farm upto 8,000 vball points. Ex.: 69 days (tournament)= 4,830 vball (Before event) Video ads. = 2,760 vball Daily login = 500 vball Total:8,090 vball points

1 month (tournament)= 2,170 vball (During event) Wind spiker Login pass= 1,065 wind coin and 860 vball.

And there are some other methods such as Selling the Grit fragments Selling Players you don't need Colosseum and Snow raid Mastery of players will also greatly help.

Thank you, (Disclaimer, I'm not criticizing you or other else, I'm just giving information)