I don't think this is 100% accurate, but might help people figure things out a little once they get to level 50.
This is what is available for you, and what you should be looking at, on what to start or progress on :
- Get level 50
- Complete Story : The last string of dungeons and fights are level 49 and 50, very little quests involved, so you don't have to worry about EXP either. The last three dungeons/trials are : Cape Westwind, Castrum Mediteraneum and The Praetorium. Those are 8-man contents.
- Unlock Amdapor Keep by talking to Derick Ironheart near the Waking Sands
- Unlock Ifrit Hard Mode by talking to people in the Waking Sands.
- Unlock Wanderer's Palace, an NPC behind the building of the Waking Sands.
- Start on your Relic Weapon by talking to Derick Ironheart again.
This is mostly legwork, but the next parts depends on your level of gear. Obviously you want some upgrades, so what can you do?
- -Base Item for Relic Weapon : Shortly in the Relic quest you will be asked for an item with 2 Tier III materias imbued in it. The base weapon is a potential upgrade to what you had before, but it might cost a bit considering they are high level crafts. Failing that, at least Grand Company weapon, level 44 (or 50 if you manage to clear Amdapor Keep somehow). Don't trade it after adding materias, at least not until you gotten a good replacement.
- Tomes of Philosophy : Rerun Castrum Mediteraneum and The Praetorium. 60min runs for 100 tomes is worth it. These can be traded for Darklight gear in Mor Dhona. You need a minimum of 375 tomes for accessories, which are likely to be your biggest immediate upgrade (rings, earrings, choker, bracelet, belt...). You can also run Stone Vigil and Darkhold for some 40 tomes, if it seems a bit too hard.
- Dungeons : Wanderer's Palace isn't too hard and has some gear upgrades for you, ilvl 55 or so. These tend to be better than even AF. Also 60 tomes
- Ifrit Hard Mode : Once you know the strategy, its a good source for great weapons. Once you have it you can consider trading for your relic weapon.
And what's next?
Well the relic weapon is far from done, a Dhorme Chimera fight (8-man), and an obligated run of Amdapor Keep for materials, before you get another usable weapon from the Relic quest. Amdapor Keep is some 80 Tomes of Philosophy, 40 Tomes of Mythology and some even better gear on the side.
Garuda Hard Mode and Titan Hard Mode follow, each with sequentially better weapons, but getting a few upgrades first is necessary.
Tomes of Mythology offers a new set of armors that are Job-Specific, similar to Relic Armors from FFXI. Definitely a huge upgrade, but since you can only get 300 Tomes of Mythology per week, its a long process, but something to work on at least. You also need to buy some items using these tomes for the Relic weapon quest.