What works for me is...

Adamantine: mod the minotaur card

Dragon Fang: In Disc 1, go into that little forest deal that you have the 2nd Laguna dream while on your way to Galbadia Garden. After the dream, you can roam the forest like a normal one. You will find some Grendels. These look like dogs, kinda, that are actually dragons. If they are at Level 19 or lower, they have a 178/256 chance of dropping Dragon Fangs. Or, you could do the Blue Dragon at Shumi Village thingy.

Pulse Ammo: When Esthar is being over run by Lunatic Pandora, you will find a man lying on the side of a path. I don't remember which. When you speak to him, he will do an evil weird laugh and summon an Elnoyle. Defeat it and you will get an Energy Crystal which can refined into 15 pulse ammo.

You will need the 1st issue of Weapons Monthly too.