Uhm... hint. None of the DoM / DoW end game gear allows melding materia into them. Even craftable gear allows only for a small margin of customization without any real gain, and that is only after you sunk several millions of gil into leveling crafters to 60. If you're relatively new to the game, and I suppose you are with only one class and no crafters at max level, you're better off selling DoM / DoW materia as long as people pay a decent price instead of hoarding them.