Click the covenant icon on your minimap, click the renown bar on the frame that pops up, then hover over the renown orb at the top of that to see what activities grant you renown.
By and large, you have a chance to earn renown from almost any activity: random normals, random heroic, m0, m+, raids of all kinds, pvp, torghast. If you don’t want to do torghast, low m+ is the best. Or wait a few days and just do 2-3 callings.
You may need a weekly to go 79-80, but that last one is a title only, so no big deal.
If you’re in no big rush, I’d just wait a day or two and do the callings that pop up. If you want to dish it out ASAP, go into low m+.
Some people said it was comp stomp.But i would argue that torghast is ur best bet.Especially cause you can drop the aggro as a mage and go straight for the last boss of each floar.I dont know what ilvl you are but maybe level 5 should do the trick.
If its a new account then the best bet would be to do his covenant campaign and korthia so the system can track it for his alt’s the catch up mechanics.
And after that probably playing dungeons to get some gear,or stick to korthia cause the rares drop really good gear for an 184ilvl.
My shaman got in ~2 hours comp stomp last tuesday from 66 to 79. Had to do yesterday a 1000 anima quest for the last renown. Compstomp was really efficient. Brainless but very efficient.