Here are some Job Requirements for Final Fantasy Tactics
Squire=Free

Chemist=Free

Knight=Squire Lv.2

Archer=Warrior Lv.2

Wizard=Chemist Lv.2

Priest= Chemist Lv.2

Monk=Knight Lv3

Time Mage=Wizard Lv.3

Oracle=Priest Lv.3

Summoner=Time Mage Lv.3

Mediator=Oraclelvl.3

Geomancer=Monk Lv.4

Thief=Archer Lv.3

Lancer=Thief Lv.4

Ninja=Archer Lv.4, thief Lv.5, Geomancer Lv.2

Singer (female only)=Mediator Lv.5, Summoner Lv.5

Bard (male only)=Mediator Lv.5, Summoner Lv.5

Samurai=Knight lvl. 4, monk lvl. 5, Lancer lvl. 2

Mathmatician=Priest lvl.5, Wizard lvl. 5, time mage lvl. 4, Oracle lvl 4.

Mimic=Knight Lv.8, Chemist Lv.8, Summoner Lv.5, Mediator Lv.5, Geomancer Lv.5, Lancer Lv5

That's pretty much all the abilities
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