Forget about reputations, they take way too much time and provide some absolutely awful rewards, inferior to almost anything else you can get as a level 80.
First, level up a gathering profession and start farming materials, then sell them in the Auction House. Keep doing that as much as possible. Mining or Herbalism for example. With the gold you get, buy yourself the best level 200+ epic items for each equipment slot from the Auction house.
Second, try to join a guild, cry and beg and humiliate yourself to the point where people start giving you free items and gold. Most of the players around don't need any more gold and are willing to give you some free gear. Try to steal everything you can from the guild bank and sell it in Global channel or in the Auction house.
Third, make ICC Reputation farm runs where you reserve all the loot that drops. Look for the epic level 264 BoE items. Just keep looting the corpses and collecting them while the others are killing the mobs. Don't forget to spam the Global channel that you need healers and tanks.
Fourth, start making your own raids, because nobody will probably take you as a beginner to their own ones. Ask for some achievements such as Light of Dawn or Bane, with at least 5999 Gearscore. This way you'll trick geared people into entering your own runs and carrying you, while you won't even have these achievements.