The best way to visualize this event, at least for me, is there are 2 opposite strategies. Either way will work, depends on your time and commitment.
1. You get your Druid upgrade kits through the main prizes you earn after every 25 tasks. They appear every 3 main prizes. For this strategy, you will have to go through many towns, I think 11 or 12, without opening any of the 6 chests after each town. Your pots of gold are used to hire managers exclusively, so you need to have enough to last through all these towns. Obviously you will need to spend more time into the event, as each town will require about an hour initially to set it up, and you have to check periodically every few hours.
2. The opposite strategy is you get your Druid upgrade kits via the 6 chests, with maybe 1 or 2 from the main prizes. You get one upgrade kit after you open all 6 chests, and it takes 1900 pots to open all 6 the first time you finish a town. With this strategy, you only do about 4 or 5 town, in order to have enough pots left to open the chests once after each town. This strategy is more relaxed, as you only need a couple hours to set up the beginning of each town, and then let it runs for a couple days.
I did the first strategy, and completed 11.5 towns, without any diamond, and got a maxed temple with 2 extra kits.