Ok. So this is simple.

Buy CPs and trade those for 5 dragon balls. In my server DBs cost about 13mil. But some people sell for 12.5.

So my advice for you guys is. Buy DBs from people who are selling for 12.5. And sell for 13. Even though some people will try to make you sell for less. Wait till there is someone who will buy for 13mil.

I did this and in about 1 week I earned 14mil. Just another suggestion on how to make money. Thanks:]