tomestone of poetics?

[Niwashi]

Your job quests will give you item level 90 armour, and that could suffice for a while, but the ilvl 120 (or upgraded to 130) Ironworks set that you can get from Poetics is a major boost above that. Plus it includes a weapon, which the job quests don't. This gear isn't the only thing you can get with Poetics, but it's probably the best thing you can get when you first reach level 50.

The costs are:
Weapon: 500 Poetics (or 380 sword + 120 shield in the case of PLD)
Body and Legs: 410 Poetics each
Helm, Gloves, and Shoes: 245 Poetics each
Belt and accessories: 180 Poetics each

So, completely outfitting yourself in iLvl 120 costs a total of 3135 Tomestones of Poetics. I'd prioritize the weapon first, then body, then legs, and so on down to the cheaper items, as generally the difference in power is greater than the difference in cost.
... and maybe prioritize upgrading the weapon ahead of buying some of the minor pieces.

To upgrade Ironworks (iLvl 120) to Augmented Ironworks (iLvl 130), you need either Carbontwine (for weapon or armour) or Carboncoat (for accessories) for each piece. These can be either purchased for another 100 Poetics each, or if you get into the Hunt you can get them in trade for Unstained Mark Logs that sometimes drop from A/S rank marks, or can be purchased with Allied Seals. Since the gear has the "UNIQUE" tag, you cannot upgrade both Ironworks rings, so a full set would use a total of 7 carbontwine and 4 carboncoat.



The weapon costs 500 Poetics, but in a rather roundabout way. You buy 10 Rowena's Tokens of Poetics for 40 each, and an Encrypted Tomestone for 100 Poetics, then trade those for a weapon. (Back when it was endgame, the Encrypted Tomestone was exclusively a raid drop, and I suppose it's still available there, but they gave us an easier way of purchasing it once level 50 was just a mid-game point to pass through. Rowena's tokens were originally a lot more expensive too, and were a way of splitting up the cost of something that took more tomes than you could hold at a time.)