Gold
Gold is currency of Idlescape. Many players call it coin, GP, or money.
Acquisition
You can obtain gold by vendoring most items, by trading with players in the marketplace, by opening chests, as a loot from some monsters killed in combat and for getting resources while affected by Scroll of Wealth enchantment.
Use
Gold is used to buy items from in-game shop or player driven marketplace. Because of that, in non-ironman mode most items can be bought with gold, with the exception of the untradeable Corrupted Ring and some event items.
Gold sinks
Some significant gold sinks are the 5% fee on items sold in the marketplace and also the Shrine of the Toucan. Glove shop also removes money from the game but is far less significant.
Gold in economy of Idlescape
Amount of gold in game economy and its distribution amongst players is known only to developers. Rough estimation of order of magnitude can be made by looking on marketplace offers, where some endgame items are priced up to a 5,000,000,000 gold.
Trivia
According to [INFO], Habs is the richest player in Idlescape.
Money values appear white when under 1 million, pale blue when over 1 billion, and a light green in between.