User blog comment:TheScottBird/I Need Some Help/@comment-24145588-20140929232702

I haven't seen it mentioned anywhere yet, but I would also strongly recommend getting a Unity Tree on each of your islands. I would put this even before the Mini-Mine. The Unity Tree will make it much easier to get your monsters to 100% happiness, because you will not have to worry about buying multiples of decorations, and trying to cluster them around the right monsters. You also won't have to worry about how to group your monsters, and if you do have some of them in a Hotel (which is likely, when you have the small castles), they will still contribute to other monsters' happiness.

The million coins for the Unity Tree may seem expensive at low levels, but when you consider what you will save on decorations, and how much faster your monsters will produce coins, it will pay for itself very quickly. I put it ahead of the Mini-Mine in priority because I don't find diamonds to be very useful, except for some of the castle upgrades. Monster happiness seems to be a higher priority at low levels.