As Fina advises, buying doubles of the Ironworks stuff to then exchange for GC Seals that have a bit more versatility is a good move.

As is buying the Unidentifiable Ore, Bone, Shell and Seeds which will be required later on for Anima Weapons (20 of each paired with 4 each of the Kingscake, Adamantitie Francesca, Dispelling Arrow and Titanium Alloy Mirrors you can buy with GC Seals).

Also if you're only at ilvl 120, I'd recommend buying the Carbontwine and Carboncoat items, which can be used to upgrade your Ironworks gear to 130 by the NPC Drake (Found in the North Shroud).