General question about the game.

I have been playing this game for a few months, kinda blindly. I have a few good characters that can be dokkan. But I'm stuck where I need to do the dokkan events, and can't successfully do them without using a ton of stones. I tried looking at the guides on here and I run into one of two problems. I don't have all the characters in the guide to battle easily, or my team cost is too low. Most of the time it is the first problem. Is there a specific level I need to be before I can attempt a dokkan event without using a ton of stones? Also are there alternative guides to beating these events if I don't have the top tier units(ssj3 goku it seems)?

Sorry if this is in the wrong section.