Premium

In the Premium tab, you can purchase Credits.

Credits can be used to build a Clan, upgrade Clan buildings, purchase Boosts, and purchase Autos.

Boosts are the following:

Combat Exp Boost - Up to 150%

Gathering Exp Boost - Up to 150%

Crafting Exp Boost - Up to 150%

Gold Boost - Up to 150%

Attribute Boost - Up to 150%

Mastery Boost - Up to 150%

Drop Boost - Up to 75%

You also gain Titles for purchasing credits, and the thresholds are as follows (courtesy of Hazzy):