I think you have the concept of expansions wrong.
The different expansions do not require one another. The original Everquest, Ruins of Kunark, Scars of Velious, Shadows of Luclin, Legacy of Ykesha, Planes of Power, Lost Dungeons of Norrath, Gates of Discord expansions are all independant of one another, and none of them include the previous ones.
Meaning, if you purchase GoD, you will still lack Velious, Luclin, Ykesha, PoP and LDoN. Do what someone else suggested if you want the full experience, and buy the bundled pack that includes all the prior expansions. It's dirt cheap, and even though it includes the original EQ and Kunark, you can just integrate it to your current account. You'll keep all your characters, have the same login, but will add on any of the accounts in the bundle that you lacked previously.
Adding an expansion to your account only enables certain zones and features of the expansion, it's not a unique game. Buying Planes of Power will bump the maximum level to 65, add some new AA abilities you can get, and of course, the new zones. Same account, same characters, just more to do.
As far as GoD goes, it doesn't matter a ton whether you buy it in-store, or order it online. The in-store version comes with a little ornamental staff, as well as giving you one in-game. Same thing with LDoN, except it was a keychain, and an in-game weight-reduction bag.
Edited, Fri Feb 13 23:02:22 2004 by Branaddar