Several new members were asking this so I am going to post it here for reference!

Job > Class > Requirements (one specific job to 15 before starting job quest).

Paladin - Gladiator lvl 30+, Conjurer lvl 15+

Monk - Pugilist lvl 30+, Lancer lvl 15+

Warrior - Marauder lvl 30+, Gladiator lvl 15+

Dragoon- Lancer lvl 30+, Pugilist lvl 15+

Bard - Archer lvl 30+, Conjurer lvl 15+

White Mage - Conjurer lvl 30+, Gladiator lvl 15+

Black - Mage Thaumaturge lvl 30+, Pugilist lvl 15+