Once you reach 110 you will receive a few quests. One will be to go back to your order hall and speak to someone. This person is an armor vendor. Every armor piece sold has some requirement to it. Some are reputation based while others may require defeating certain enemies or completing quests. The initial quest to speak to this person will reward you with a new helm.
The next piece of armor to work towards from that vendor is the legs. The requirement for these is to kill the final boss in each of the dungeons on any difficulty. The bracers are also easy enough to get just by working through the order hall campaign. From there though the requirements for new gear gets a bit harder to complete.
One of the other quests you receive upon reaching 110 is for the world quests. These are very important because they provide a multitude of rewards. These rewards can be artifact power ups, gold, professions patterns, order hall resources, or gear. To unlock world quests you need to have obtained friendly reputation with all of the Legion factions. Four of the five necessary reputations you should have past friendly just by leveling through the zones. The final is the Nightfallen in Suramar. Getting this reputation to friendly takes under an hour so shouldn't be much of a hurdle.
The gear rewards from world quests reward ilvl 805+ gear. Since the likely item level you'll have when reaching 110 will be closer to 780 these should provide considerable upgrades. There will be times that there are no gear quests to get so don't plan to farm them all day to get geared up.