The fastest way to earn Justice Points is by running dungeons

Things don’t stop at 496, either. Particularly lucky (or persistent) players might find themselves in possession of a Burden of Eternity, an extremely powerful artifact that,  Little Empire Mojo when used on a Timeless armor token, causes it to create an even more powerful item rated at ilvl 535. Get your hands on a few of those pieces and you should be more than prepared to participate in the Siege of Orgrimmar raid.
Your Reputation Precedes You
Of course, the Timeless Isle isn’t the only way to gear up. As of 5.4, we’ve made some big changes to the older ilvl 489 reputation gear—that’d be the Golden Lotus, Klaxxi,  Buy Little Empire Mojo August Celestials, and Shado-Pan gear. All of this gear is now available for Justice Points regardless of your reputation with the respective factions.
The fastest way to earn Justice Points is by running dungeons (particularly Heroic dungeons), but they can be earned through Scenarios and even converted from Honor points if you prefer (though you’re probably better off just buying the Honor gear . . . more on that later).  Cheap Little Empire Mojo Once you’ve got some Justice Points saved up, head off to the quartermaster at Niuzao Temple in Townlong Steppes to get some sweet, sweet epics.
Valor Points still have their place as well. For just 250 Valor points, you can add four Item Levels to a piece of Epic gear, and you can upgrade any piece twice. If you’re looking to gear up in a hurry, that’ll probably give you the most bang for your buck. Even if you don’t have anything you’d like to upgrade just yet, it’s likely more worthwhile to hang onto your Valor until you do.

Or Maybe Just Stab Someone