I'm trying to figure out how to build my virtual economy. It seems like some games have one currency and some of them have up to 3 and 4 different ones.
The game is an action game which is currently single player but I'm planning on adding a tournament mode that allows users to compete against each other. The virtual goods that a user would be able to purchase would be either customization to the character or powerups and utilities that give the character more abilities in the game. The character is able to gain coins during game play.
The advice I'm trying to get is whether or not it makes sense to set up more than one currency and more than two currencies? What are the pros and cons?
Reference to some resources that indicate research would be great.
Single Currency - usually simpler for players to understand
Multiple Currencies - allows more flexibility to in future optimizations
For a single player action game I don't think you need more than two. Three of four currencies is something that is usually reserved for resource management games where you actually gain different types of supplies and currencies as part of the game play.
A standard two currency model for an action game is having a 'soft currency' and a 'hard currency':
Soft Currency - Coins that a player can collect or otherwise obtain during game play
Hard Currency - Only available to users who pay real cash
The game would normally allow users to exchange hard currency to soft currency but not the other way around. To get more users to pay some virtual goods will require a user to pay with hard currency or with amounts of soft currency that are hard to collect with game play.
There are different reasons to incorporate single and multiple currencies.
Single currency is a simple way to trade. Just like in real world we created it not to go from vendor to vendor, because one sells carrots we want, but he wants potatoes in exchange, and we have only oranges. So we need to look for a vendor that will trade oranges for potatoes, or oranges for anything else that someone else will trade for potatoes, or for something else that another trader will exchange for potatoes or... You get the idea.
Make your game more complex. Think of a chess game with only two pawns - players will get bored quickly. With multiple currencies you make a player think what currency he might need to get for best results, e.g. should I get more imperial credits for a new ship, or rather concentrate on collecting bottle caps to get illegal upgrades from Rogue Junkers.
Currency is wealth, wealth is your position in society, that is, your rank. You may divide different game mechanics to multiply not exchangeable currencies to create separated rankings.
A popular multiple currencies system is free/premium. One currency, e.g. gold, can be achieved by trading with others, or found in game world, the other only bought.
You may enable multiple currencies in different countries/fractions with an option to exchange them, to simulate a high level economy like in real world, where players can make money by buying and selling in a right time.