I know you've been given a lot of hints already, but here's a couple of tips too. Go through the Forbidden Land of Eureka first. That place is probably the hardest part. You'll take a lot of damage and you'll need to use Cure spells a lot. Hopefully you won't run out of them. Don't open any chests yet, just make it to the end where you get Ninja and Sage classes. Then change to them (I'd recommend two Ninjas and two Sages) and heal yourself on the healing springs.

The Shurikens cost 65,000 gil, and if you equip both Ninjas with double Shurikens, that means you'll spend 4 shurikens, i.e. 260,000 gil, on one turn if they both attack. You can get a lot of money by leveling up in Eureka. Go and get the treasures of Eureka and defeat the bosses guarding them. They shouldn't be too hard now that you have Ninja and Sage classes. Buy some Shurikens when you can afford them, 14+ should be enough.

When you've leveled up, walk through the Sylx Tower and different branches to get all the treasures, though before you go to the room-of-no-return (you'll know when you've reached it since the music stops playing there, and you can still exit the room unless you've wandered too far in the room), you may want to make your way back to the Airship or the healing springs of Eureka and also save your game.

Fight your way through Sylx again, it should be easier on the second time. Defeat Zande by having your Sages cast Haste on your Ninjas on the first turn while Ninjas attack, and have Ninjas attack while Sages use Bahamut or other strong spells or summons. Zande might die before he gets to cast a single spell on you, and you don't even need to use the Shurikens yet. Don't worry about the next battle, you'll lose it anyway.

When you're in the dark world, get the Ribbons (if you already have one, you'll only need to get three of them). ZandeClones are easy to defeat if your Sages both have staffs that petrify the enemies. Just have them attack, and the ZandeClone is defeated. Cerberus shouldn't be too hard, just Haste the Ninjas and have them attack while Sages cast offensive and healing spells. Go to the back row when fighting the two-headed dragon. He can only attack one character at a time, and he can't kill anyone with one hit if you're on the back row. Don't bother with Shurikens, just Haste your Ninjas and have them attack (they'll still do some pretty good damage) while Sages cast Cure3/4 spells.

Echidna and Ahriman are the hardest bosses, especially if they cast Meteo. Use the Shurikens on these. If you want, you can cast Haste on Ninjas before they throw their Shurikens, but just a word of warning: after tossing the Shurikens, you'll need to re-equip new ones, and at least to me Haste wears off when you re-equip your Ninjas. This means that if the Sages manage to cast Haste on your Ninjas and they use their Shurikens, they'll probably do 9999 damage, and when you re-equip them, the Shuriken damage goes back to 5000-6000. But if the Ninjas throw their Shurikens and Sages cast Haste on them after that, casting Haste will be useless as they'll just keep doing 5000-6000 damage. It's up to you. I'd probably just keep casting Cure spells, Bahamut and spells with my Sages rather than casting Haste.

Quote Originally Posted by Elpizo
Those Shurikens, do I need to use them on Ahriman, Echidna, Cerberus and 2-headed Dragon or do I need to spare em all for Cloud of Darkness?
I think Echidna and Ahriman are the hardest bosses, so I'd save my Shurikens on them. Dark Cloud is easy in a way that she(?) has only one attack. If you have Shurikens left, you can use them on her, but I can defeat her without any Shurikens. Here's how:

Turn 1 - Ninjas (with normal weapons) attack, Sages cast Haste on the Ninjas.
Turn 2 - Ninjas (with hasted weapons) attack, Sage1 uses Cure4 on himself, so does Sage2.
Turn 3 - Ninjas (with hasted weapons) attack, Sage1 uses Cure4 on Ninja1, Sage2 uses Cure4 on Ninja2.
Turn 4 - See Turn 2.
Turn 5 - See Turn 3.

And so forth, until Dark Cloud dies. It shouldn't take too long. If you need to use Elixirs to restore your HP or MP, go ahead since this is the final battle. Good luck with the final dungeons! You'll need it, or Echidna and Ahriman's attacks will destroy your party (two Meteos on a row = game over). When you beat Dark Cloud, enjoy the ending after that. ^^