Players can get rep with all the mini factions in Cataclym from doing dungeons wearing their tabard or doing their daily quests.
Every faction has some epic items, however the difference between the blue items and epic items is really low for now.
The best choice is to first get reputation with the faction that can give you some good blue items and specially the enchants.
For example Ramkahen gives a head enchant that has 60 agility and 35 haste, great for hunters, and any agility classes.
Wildhammer clan gives 60 strength and 35 mastery great for warriors, paladins, etc.
These enchants requires revered rep with the faction, revered is the last stage, then comes exalted that gives epic items.
At least for hunters the best faction seems to be earthen ring for epics, there is a nice dps ring there. Before I suggest getting rep to get the enchants. Same for other classes, check the quartermasters for all the factions and see what items they get, after you get the enchants, start getting reputation for epic items.