What to do at level 50?

[Estellios]

Do yourself a favor and pick up the level 50 Grand Company Lieutenant weapon unless you already have a weapon with an item level higher than 55 (item level is super important from this point on). It should last you until you get your relic finished or a primal weapon and you don't have to deal with random drops in Wanderer's Palace or Amdapor keep hoping for it to drop. Artifact (AF) gear is fine but you should work on updating it through dungeon runs and saving up Allagan tomestones as people have been suggesting.

Concerning accessories: Upgrade them immediately as you will need to have minimum item level for specific content and having really outdated stuff may become an issue. There are no Artifact accessories so my recommendation is to go to the market boards and splurge on the level 48-49 accessories (Rubellite) and the item level 55 militia or Imperial Operative accessories that have Strength on them. If possible you should get the high quality versions as not only will they have better stats, they will spiritbond faster and when you replace them you may be able to get materia to sell or use for your relic quest.