Basically the way to deal with any content in the game comes down to understanding, and/or doing a few main things.

1. BDM is really more of a resource management game, than a RPG, as such success in it comes down to your effectiveness in getting, and using resources, including time, with some good luck also being helpful due to RNG elements.

2. Log in everyday, do all the available tasks, and leave a character in to auto farm for you as much as possible.

3. Like the vast majority of service based games, of any platform, and especially free to play ones, they are largely made to just make the companies involved money, so can include various ways for you to throw money at it, which will help you in game.