If all of your builders are busy, and you want to move on to a new upgrade or building, you have two options: you can either spend gems to instantly complete the construction and free up your builder, or you can use gems to buy another Builder's Hut (unless you've already reached the maximum of five huts).

In this example, the Army Camp costs 2500 in elixir and there is no elixir in the storage.You will see a pop up asking if you wish to use gems to purchase the missing elixir.

By accepting, you spend gems to start the upgrade immediately. Your gems will instantly be converted into the missing resource (elixir in this case) and the upg