I haven't done the math. Maybe I shouldn't give up my "secret." I spend a minimal amount of gold by buying the little 7 gold boosts usually about 2x/day, depending on what is going on on my island. Pretty much every morning when I wake up, I have dragons that have finished breeding, dragons that have finished incubating, and dragons that have finished evolving. Of course, in the morning I also have the Quest points and the points from decorations to collect, plus usually food crops to harvest. So there is a *lot* going on first thing in the morning, so it is totally worth the boosts. Other than that I use minimal amounts of gold here and there to speed up breedings or incubations or evolutions that are almost ready but not quite. I always reach the final dragon on both of my accounts using this method, even though my newer account only has one evolution temple or whatever it is called. I do like to place in the top 6 locally and top 1000 globally if at all possible, so I will use the 2 hour boosts once they go on sale for 15 gold each. I feel like it is definitely worth that amount of gold to get the 100000 food and maps (yes, I still need maps).