but.... blood elfs are.... g.a.y.... LOL just joking : )

You need to get:
The original World of Warcraft - You can level till 60
The Burning Crusade - till 70
Wrath of the Lich King - till 80

soon to come (expected at end of this end) Cataclysm - till 85

This game you need to pay for 2 things:

1. Subscription, it is about $14 USD/month or somewhere around there
2. Each expansion you buy including the original World Of Warcraft.

It is expensive but worth it. There is a reason why 1 out of every 1000 people in the world plays WoW.