GZ! you reached level 110! Here is a list about what you can/should do in 7.2 after hitting max level.
1. Hit the AH
Go to the auction house and get your gear in shape with some iLvL 780 greens and 805-835 blues. Later you'll see that 780 items drop from a lot of places, including raids and they are quite much useless for those who get them so they tend to be cheap/affordable. Check both armor and artifact relic categories. You can score some good deals, like Nighthold BoE epics with 870 iLvl for 2k-3k gold.
2. Get you AK to 25
Artifact knowledge to 25 is virtually instant if you either can supply 500 order res per knowledge level or send an artifact knowledge token from your other high level character.
OBSOLETE: When you hit level 110, you automatically get the current max AK level. Everyone is at the same level and it increases every week.
3. Get your artifacts in shape
Literally one good world quest AP token can get an artifact to and over Concordance. As of 7.3.0 you don't need the Broken Shore questline to unlock Concordance. The quests were not removed however, you need them for the achievement and the Mage Tower challenges.
4. Do the Broken Shore intro scenario
Talk to Khadgar at Krasus' Landing to begin the scenario. While inside:
- stick with allied mobs: from what I saw once you attack something they start to do mad damage to those enemies
- don't run forward, unless you are a self-sustaining tank
- As of 7.3.0 you can skip the intro scenario if you completed it once at any of your characters
5. Do the AK26 quest
OBSOLETE: quest was removed, AK research is deprecated. Khadgar starts the quest from Deliverance Point after you finished the broken shore scenario. Quite painless with flying. Do the two flight-point exploration quests meanwhile.
6. Finish your class order hall campaign
I advise finishing this after you get AK26 because it awards two AP tokens which give 1M-1M AP at AK26. While you are busy enjoying the ebin five timegated order hall follower missions, do world quests. Focus on invasions and broken shore WQs.
As of 7.3.0 you don't need to complete your order hall campaign to unlock your 3rd relic slots.
7. Get your gear in shape
Spend the nethershards you get from invasion/Broken Shore WQs at Deliverance Point for 850+ epic welfare gear (they all have the usual chance to warforge/titanforge). NOTE: trinkets and rings are Unique-Equipped so don't waste your shards on two tokens from these for the same spec as you cannot equip two dauntless trinkets/rings.
Certain enemies and Argus-related emissary rewards drop BoA items you can send to your alts. On Argus there is a new currency you can spend on new item tokens.
Nethershards now can be used to buy follower XP and iLvl boosts at the Broken Shore. The Relinquished vendor was removed.
8. Start raiding, heroics and mythic
If you pass iLvl 825 you can start doing LFR and heroic dungeons. However with Dauntless items you can go above 840 easily and start doing mythic0 dungeons too.