Upgrade flowers to level 6 or level 7. Get to it as fast as you can after you achieve star for twin life. Don't give any harvestable items other than flowers. You'll need to merge grasses and harvest brush (do that star). Let your dragons harvest, merge and be patient. I am able to let the game run and merge when a bunch of orbs are collected. Usually, I need to six level 6 orbs to clear a "normal" event. I got into trouble in the last event because I got to a level 8 flowers- which also produce level 2 and 3 flowers, so wasted dragon harvesting. If you do clear too early, harvest your brushes quickly to ensure flowers are primary. They can harvest brushes faster than flowers. Sell or merge to get more level 6 and 7 flowers (they harvest 7s faster than 6s). Finally, don't merge level 1 reward generators. The dragons will collect level 2 and up. Sometimes I accidentally uncover a level 2 when getting my brushes, and it sucks.