Welcome to 80.
Yes, you absolutely want to be doing heroics to get
Emblem of Conquest, which can give you great gear. Do the Daily Herioc and also get a couple
Emblem of Triump, that can give you an even better piece of gear once in a while.
Along with these great rewards, you can get upgrades from the boss drops themselves in Heriocs. Rep rewards should also be looked at. Use
Atlasloot so that you have rep reward information at your fingertips and pick some items you want to work toward. Look up the
rep factions and do some research on quest chains for them. Pick a couple factions and start working on them. Get their tabard when you can and wear it in dungeons you do.
If you have a profession that can craft gear, look into epic items you can make for yourself. When I was a fresh 80, I also picked up a few BOE epics from the AH to get me started. Although today, there are so many other easy ways (emblems) to get them, don't spend alot at the AH, unless it is a piece that isn't easily replaced.
When you can, get into a Naxx group. Hopefully your guild does some runs. Look up some info on the bosses before you go in. If you don't do anything else, know about the "safety dance" in Naxx before you need it (says the priest who just hopped around in a pug the first time).
Basically, there are multiple ways to get your epics. Turn on the showing of your gear's ilevel in your interface options, and try to up the ilevel of each of your slots. When you get a nice epic,
gem and
enchant it.
Hope that gives you a start. Gratz on 80.