FX is the in-game currency that can be used to purchase various items, music packs, and more. There are many ways you could obtain it outside of purchasing it outright with real money. Some examples would be participating in challenges within their game world for free coins which will give you up to 50% off your total coin cost for a week or collecting tokens from playing minigames on Playstation Network games like Tennis World Tour 2 or The Last Of Us Remastered.