Jobs, Disciples of War
To become a Paladin, you must level your character to Gladiator Level 30 and Conjurer Level 15 and complete the Paladin's Pledge quest for the Gladiator's Guild. Paladins are essentially Gladiators whose attacks have become infused with magic. They can be played the same way - they will simply deal much higher damage.
To become a Monk, you must level your character to Pugilist Level 30 and Lancer Level 15 and complete the Brother from Another Mother quest for the Pugilist's Guild. With this job, the Monk's hand-to-hand attacks will deal greatly increased damage.
To become a Warrior, you must level your character to Marauder Level 30 and Gladiator Level 15 and complete the Pride and Duty (Will Take You from the Mountain) quest for the Marauder's Guild. A Warrior is an even tougher tank of a Marauder, with more skills that increase damage given and decrease damage taken.
To become a Dragoon, you must level your character to Lancer Level 30 and Marauder Level 15 and complete the Eye of the Dragon quest for Ywain in Old Gridania. Dragoon's will learn abilities that greatly increase their combat prowess and maneuverability.
To become a Bard, you must level you character to Archer Level 30 and Pugilist Level 15 and complete the Song of Bards and Bowmen quest for Luciane in New Gridania. Bards go far beyond the long range firing support of Archers. They gain abilities to buff the party as well as increase their personal damage dealing.