Believe the message. The iPod need 4.5 GB available to install that app.
To download/install an app directly to the iPod you need available storage equal to about three times the file download size. Syncing the app to the iPod requires a lot less. Thus you either have to free up more storage or sync the app from your computer.
Update your ipod/iphone/ipad, install latest iOS, leave your device connected to the computer, download the app (Fifa 13) in itune store on your PC/MAC. Now copy the game to your device, press 'apply' at the right lower corner of the screen and then press 'done' at the right UPPER corner of the screen when it is completed. Spent hours and hours on downloading without all these steps, almost gave up, glad to find this solution.
Press like if you are successfull:)