Drop a lot of trash loot
If you decide to go grinding on mobs to make dragon ball gold, which I usually do if I need a couple of thousands to complete the amount of dragon ball gold for a certain item, invest in your cube first. Most of the mobs drop a lot of trash loot, which usually is food for the vendors, but in most of the cases you will get nice dragon ball gold by selling this type of loot. So, it is best not to destroy the grey, useless loot, because that would be a waste.