The Wealth Temple holds the Divine Powers responsible for improving the economy of your city.
Every upgrade of the Wealth Temple will unlock some new Divine Powers to be researched. To be able to conduct research in the Temples, you need to get enough Elixir. That you can get either by generating it in the Sanctuary, or from the Shrines which randomly show up on the map after killing beasts.
The Wealth Temple itself does not provide any special bonus other than providing a place to research Divine Powers.
* Total Power amount provided on each level