I loved Golden Sun. I want Golden Sun 2.
As far as Psynergy and Djinn go, it is a bit complicated, but you can mix and match different elemental djinn to create super classes. I’ve found the ultimate classes for the final battle.
Issac: Samurai - 3 super supportive Psynergies: Angel Spear (raises attack for all), Protector (raises Defense for all), and Magic Shield (raises resistance for all) - Give him the Silver Blade for the final battle because the Water Attack does a good deal of Damage to the Fusion Dragon. (4 Mars and 3 Jupiter needed)
Garet: Dragoon - Ply and Wish series spells and Cutting Edge, a water based spell that does good damage to the final boss. - If you have the Cleric’s Ring, give it to him along with the Muramasa, Thunder Crown, and Demon Mail. The Ring will remove the effects of the curse, though you’ll still be cursed. (3 Venus and 3 Mercury needed)
Ivan: White Mage - Wish series spells and revive. Prism series attacks and Resist. (3 Venus and 4 Mercury needed)
Mia: Scholar - Wish and Prism series attacks, along with High Impact. (3 Mars and 4 Jupiter needed)
Garet, Ivan, and Mia all have wish spells and good water based attacks, while Issac has awsome support magic and the Silver Blade does a good deal of water based damage as well.
Also as a side note that if you want the best protection for Mia and Ivan, put them in the corners of the line. Here is what I mean:
Ivan, Issac, Garet, Mia
Chances are spells are gonna focus on one of the middle characters more (the iIi format is what I’m thinking of). If they want more people to get hit, they’re gonna aim for the middle, and with this format, it is either Issac or Garet.