Hi there friend,
My main class is tank (PLD). My advise to you right now that you are at level 50, is to do all the Job Quests for the class & win the artefact armour, it's free and you don't need to use your Gil in MarketBoard&NPC's. You should also do Daily Duties and Dungeons to farm poetics. For example, using the artefact armour, the first poetics that you gain you use to buy in Mor Dhona lvl120 accessories, than when you got all the acessories, you use them to buy lvl120 armour. That gear and accessories can be upgraded to lvl130 armour using Carbontwine and Carboncoat. Don't worry using poetics, you has a new player, will receive bonus tomes when entering a new trial/dungeon/raid etc.
The new Dungeons will also give armour/acessories/weapons. Has a tank is important that we have the best gear possible, because you need HP&Agroo.
Cheers my friend.