The game has online and offline co-op/competitive playlists. Single player customization includes lots of control over game types, Forge world, and a custom Spartan outfit (Credits are needed to purchase gear, which are easily obtained through daily/weekly challenges doable offline or going online and playing with/against other people.) If you plan to stay off Gold membership, then the DLC is not worth it. If you plan on getting Gold, then the DLC is not needed, even though it says it's recommended.