Dark Matter????

[hockeydude]

im still kinda new to final fantasy. i have only played ffx and ffx-2. right now since ffx is the only game that works on my ps2 iv been working on the side quests and stuff like that. i want to make my own weapons because i cant find all the celestial ones. and im just wondering how to get more dark matter. having it says you need dark matter to make weapons break the damge limit. HELP ME OUT!!!