After level 29 in a craft you can attach materia to armor that have no empty materia slots, but the chance of failure is high.
To clarify, after getting Advanced Melding, you can attach materia beyond the guaranteed, 100% success rate "green" slots, up to a maximum of 5 total materia. But that requires that the item has green materia slots to begin with. Gear that does not have those green slots cannot have materia melded to them, even with Advanced Melding.
Lyonheart, like Eorzia, will be reborn in FFXIV!
FFXI veteran (Lyonheart and Lakiskline of Lakshmi)
1/467 on signed HQ Weskit!!!