MetalIllness
Criminally Insane
Of course, the keys itself do not have a level/faction requirement, although you have about 50% chance that a hostile mob will spawn who will attack you. No reputation then, the other 50% chance you'll spawn a friendly NPC, who will give you rep for the faction it belongs to.
Among them are the Consortium, Sporeggar, Sha'tar, Lower City, Cenarior Expedition and the Keepers of Time. Taking the amount of luck to spawn a Cenarion Expedition related mob into consideration, you'd roughly need 4000 keys, although with more luck, you might only need about 800 keys.
Level 1 with Keepers of Time tabard's also nice.
Among them are the Consortium, Sporeggar, Sha'tar, Lower City, Cenarior Expedition and the Keepers of Time. Taking the amount of luck to spawn a Cenarion Expedition related mob into consideration, you'd roughly need 4000 keys, although with more luck, you might only need about 800 keys.
Level 1 with Keepers of Time tabard's also nice.