Gold, being the less abundant resource for most people playing Civony, is a must to have for upgrades and as a higher level player for research in the academy.
The amount of gold you will recieve per hour is determined on your tax rate and population. (Population * Tax Rate)
Gold can be transfered amongst players, via the transport option. Gold can be used to buy more resources via the market and is also used abundantly for upgrades in the academy. Also note, that in order to be promoted to a new rank or title, a certain gold limit is needed.