You can wait until you hit level 30 but to be honest they are bundling it with the rest of the xpacs now and you can get the whole shebang on steam for like 10 bucks. If you are a 360 player I think they did put together an abyssea collectors edition for that too but it might be harder to get hold of new. But what you can do is just buy a cheap used copy for the installation of the base xpacs, and then buy the steam copy for the game codes. The game codes will work on all three platforms so it doesn't matter that its for PC. If you can pick up a copy of the older collectors edition used for cheap, then go that route because it will just download the Abyssea sh*t anyway.
Here's that link to a really nice PDF a guy put together for abyssea. Abyssea thread
Just make sure that once you hit 30 you unlock it so that its building your stones while you do other sh*t in the game and it will be ready for you to jump right in when the time comes. Edited, Feb 6th 2012 10:52am by Torrence