Upgrading U/U items to make them better.

[Shneibel]

But unless they plan to add better gear you can buy with GC seals its pointless, all the lvl 50 GC gear is crap.

not all of them, if you check all the gear:

craft pants +15 craftsmanship (you can survive w/o but with it you can use another piece of gear for more M craftsmanship)

the 3 shield (grid got the best block rate of 168 or so while Uldah got the best dmg reduce and the LL is both and give +10 atk power)

2 rings

Chocobo gear at 1.21 (useless, but they will be decent at 2.0 and you cant craft them, only buy from GC)

end of the line: look at the vision the game is heading

edit : forgot the shield at grid as well +10 m accuracy, decent for THM