In Final Fantasy 5, as you progress throughout the game you'll gain Job crystals from hte shards of the elemental crystals. As you chose fight as a certain jobclass you'll gain AP from it and learn abilities specific to that class, you can change job classes whenever you want. Once you master a job class [by getting enough Ap] you'll be able to use all of the inate commands you would have had with that job class when you're set on BARE [no job class] for example, after you master the Knight job class, you will be able to equip Swords, Shields, when your set on Bare. So eventually Bare and Mime wil be your two best classes.

Name        [How to get job class]
Default Command
Desrciption
Job LV    Name    AP Needed    Type    Effect

Knight
Monk
Blue Mage
Thief
Black Mage
White Mage
Berserker
Sorcerer [Sword Mage]
Time Mage
Summoner
Red Mage
Trainer
Geomancer
Ninja
Bard
Hunter [Archer]
Samurai
Lancer [Dragoon]
Dancer
Chemist
Mime
Job Class Reference Charts

Knight        [Found in Wind Crystal Shrine]
Default command: Guard
Masters of the sword. High Offensive and defensive power but no magic ability whatsoever.
Lv1    Cover    10   [Auto. Battle] Protect an ally with low Hp
Lv2    Guard    30   [Command]    Protect self from any Phys. damage
Lv3    2-Haded50   [Automatic]   Use both hands to increase weap. Pwr.
Lv4    Eq.Shld    100 [Automatic]    Can equip Shield regaurdless of class
Lv5    Eq. Armr150[Automatic]    Can equip Armor regaurldess of class
Lv6    Eq. Swrd350[Automatic]    Can equip Sword regaurdless of class
Total Ap needed to master class: 690

Monk        [Found in Wind Crystal Shrine]
Default command: Store
Experts at Martial Arts. They have the highest Vigor [Strength] in the game, and don't require weapons to deal out a large ammount of damage.
Lv1    Store    15   [Command]     Charge power for double dam. next turn
Lv2    Barefist    30   [Automatic]        Gain same Vigor as a Monk
Lv3    Chackra45   [Command]     Restores soem Hp plus abnormal stat.
Lv4    Counter 60   [Auto. Battle]  Counter att. sometimes when phys. hit
Lv5    Hp+10%100[Automatic]        Increases Maximum Hp by 10%
Lv6    Hp+20%150[Automatic]        Increases maximum Hp by 20%
Lv7    Hp+30%300[Automatic]        Increases Maximum Hp by 30%
Total Ap needed to master class: 700

Blue Mage    [Found in Wind Crystal Shrine]
Default command: Blue
Mages that can learn and use the skills of their enemies. A bit stronger physically than most other mages.
Lv1    Check    10   [Command]      Check enemy's Hp and weakness
Lv2    Learning20   [Auto. Battle]   Learn enemy skill reguardless of class
Lv3    Blue       70   [Command]      Use Enemy Skill regaurdless of class
Lv4    View    250 [Command]      Check enemy's Hp/Weak/ Condition
Total Ap needed to master class: 350

Thief        [Found in Wind Crystal Shrine]
Default command: Steal
Swift characters that can steal Items from enemies in battle. Fairly weak physically and have no use of magic or special skills.
Lv1    Secret    10   [Auto. Map]     Can see hidden passages
Lv2    Flee    20   [Command]     Escape very quickly from battles
Lv3         Dash    30   [Auto. Map]     Hold O [on PSX version] to run
Lv4    Steal    50   [Command]     Steal items from enemies in battle
Lv5    Caution  75   [Automatic]     Protect against back attack
Lv6    Mug       150 [Command]     Steal item from enamy and harm them
Lv7    Footwrk 300 [Automatic]     Gain same speed as a Thief
Total Ap needed to master class: 635

Black Mage    [Found in Wind Crystal Shrine]
Default command: Black
Battle mages. Use offensive magic to deal large ammounts of damage. They are extremely weak physically.
Lv1    BlackL1    10   [Command]       Can use Level 1 Black Magic
Lv2    BlackL2 20  [Command]          Can use Level 2 Black Magic
Lv3    BlackL3 30  [Command]          Can use Level 3 Black Magic
Lv4    BlackL4 50  [Command]        Can use Level 4 Black Magic
Lv5     BlackL5 70  [Command]           Can use Level 5 Black Magic
Lv6    BlackL6 100[Command]          Can use Level 6 Black Magic
Lv7          Mp+30%400[Command]       Increases Maximum Mp by 30%
Total Ap needed to master class: 680

White Mage    [Found in Wind Crystal Shrine]
Default command: White
Recovery mages. Use defensive magic to recover and aid allies. Liek Black Mages they are also extremely weak physically.
Lv1    WhiteL1 10   [Command]       Can use Level 1 White Magic
Lv2    WhiteL2 20   [Command]       Can use Level 2 White Magic
Lv3        WhiteL3 30   [Command]       Can use Level 3 White Magic
Lv4    WhiteL4 50   [Command]          Can use Level 4 White Magic
Lv5    WhiteL5 70   [Command]          Can use Level 5 White Magic
Lv6    WhiteL6 100 [Command]       Can use Level 6 White Magic
Lv7    Mp+10%300 [Command]          Increases Maximum Mp by 10%
Total Ap needed to master class: 580

Berserker    [Found in Walz Tower]
Default command: None [Berserkes so can't use commands]
Very strong warriors that are constantly berserked. They have the highest attack power out of any job class.
Lv1    Berserk  100 [Auto. Battle]     Att. continously, despite your class
Lv2    Equ.Axe 400 [Automatic]       Can equip Axe regaurdless of class
Total Ap needed to master class: 500

Sorcerer [Sword Mage]    [Found in Walz Tower]
Default command: Sword
Mages that cast elemental and status invoking spells on their swords. They are physically stronger than any other kind of mage and extremely useful.
Lv1    MagWal 10   [Auto. Battle]       Auto. cast MBarrier when near KO.
Lv2    SwordL1 20  [Command]          Can use Level 1 Sword Magic
Lv3        SwordL2 30  [Command]          Can use Level 2 Sword Magic
Lv4    SwordL3 50  [Command]          Can use Level 3 Sword Magic
Lv5    SwordL4 70  [Command]          Can use Level 4 Sword Magic
Lv6     SwordL5 100[Command]          Can use Level 5 Sword Magic
Lv7    SwordL6 400[Command]          Can use Level 6 Sword Magic
Total Ap needed to master class: 680

Time Mage    [Found in Walz Tower]
Default command: Time
Time and space mages. Use mainly use magic that is neuther recovery or offensive.
Lv1    TimeL1    10   [Command]           Can use Level 1 Time Magic
Lv2    TimeL2  20   [Command]              Can use Level 2 Time Magic
Lv3    TimeL3  30   [Command]           Can use Level 3 Time Magic
Lv4    TimeL4  50   [Command]           Can use Level 4 Time Magic
Lv5    TimeL5    70   [Command]              Can use Level 5 Time Magic
Lv6    TimeL6    100 [Command]              Can use Level 6 Time Magic
Lv7    Eq. Rod    250 [Automatic]              Can equip Rod regaurdless of class
Total Ap needed to master class: 530

Summoner [Caller]    [Found In Walz Tower]
Default command: Summon
Expert mages that can summon mystical creatures for both offensive and defensive effects. They are physically, the weakest of all the job classes.
Lv1    SumnL1 15   [Command]           Can use Level 1 Summon Magic
Lv2    SumnL2 30   [Command]              Can use Level 2 Summon Magic
Lv3    SumnL3 45   [Command]              Can use Level 3 Summon Magic
Lv4    SumnL4 60   [Command]          Can use Level 4 Summon Magic
Lv5     SumnL5 100 [Command]              Can use Level 5 Summon Magic
Lv6    Call     500 [Command]              Call random mon. without using Mp
Total Ap needed to master class: 750

Red Mage    [Found in Walz Tower]
Default command: Red
Mages that can use both Black and White magic, however they can only use the first three levels of each.
Lv1    RedL1    20    [Command]          Can use Level 1 Black/White Mag.
Lv2    RedL2    40    [Command]              Can use Level 2 Black/White Mag.
Lv3    RedL3      100  [Command]              Can use Level 3 Black/White Mag.
Lv4    Red X2    999  [Command]          Can use Red Mag. twice in one turn
Total Ap needed to master class: 1159

Trainer        [Found in the Fire Ship]
Default command: Catch
Monster Trainers that can capture monsters when they are weakened and then release them later to aid in battle.
Lv1    Tame    10    [Command]              Can calm monsters
Lv2    Control    50    [Command]              Can control monsters
Lv3    Eq.Whp100  [Automatic]              Can equip Whip regrdless. of class
Lv4    Catch    300  [Command]          Can catch certain monsters
Total Ap needed to master class: 460

Geomancer    [Found in the Fire Ship]
Default command: Earth
Semi-mages that can use the terain that they are fighting in agianst their enemies.
Lv1    Earth    25    [Command]             Attack based on your surroundings
Lv2    Findhol    50    [Auto. Map]         Can see hidden holes on the map
Lv3    Anti-trap100 [Auto. Map]          No damage on trap floors
Total Ap needed to master class: 175

Ninja        [Found in the Fire Ship]
Default command: Throw
Steath fighters with high Speed ratings. they can equip two weapons at a time, a great skill each charatcer should learn from them.
Lv1    Dustb    10    [Command]              Escape quickly from battles
Lv2    Twin    30    [Command]          Illusion lts you evade two phys. hits
Lv3    1stAttck50    [Automatic]              Raises rate of pre-emptive battles
Lv4    Throw    150  [Command]              Throw weapons [Not Bow or Harp]
Lv5    2-Swrds    450  [Automatic]              Equ. 2 Weapons [Not Bow or Harp]
Total Ap needed to master class: 690

Bard        [Found in Chocobo Forest]
Default command: Sing
Fairly weak charcters that use songs in battle for offensive and defensive purposes. Songs take no Mp to use.
Lv1    Hide    25     [Command]         Hide to avoid taking any damage
Lv2    Eq.Harp    50     [Command]         Equip Harp regaurdless of class
Lv3    Sing    100   [Command]         Sing magic songs
Total Ap needed to master class: 175

Hunter [Archer]    [Found in Chocobo Forest]
Deafault command: Aim
Medium strength character, fairly useless besides their Sshot command which is very useful. Critter is like a scaled down version of Summon.
Lv1    Critter    15     [Command]         Calls on animal friends to aid you
Lv2    Aim    45     [Command]         Raise accuracy to a definate 100%
Lv3    Eq. Bow135   [Automatic]         Can equip Bow regaurdless of class
Total Ap needed to master class: 195

Samurai    [Found in Earth Shrine]
Default command: $toss [Gp Toss]
Good physically tough character abotu as strong as a Knight or Dragoon [Lancer]. Gp Toss can be vaery strong but consumes your money to use.
Lv1    Sslap    10     [Command]         Attack that petrifies the target
Lv2    $toss    30     [Command]         Attack by throwing Gp at enemies
Lv3    SwGrab    60     [Command]         Catches enemy's physical attack
Lv4    Eq.Kata180   [Automatic]         Can equip Katana despite class
Lv5    F.Draw    540   [Command]         Several random att. with Katana
Total Ap needed to master class: 820

Lancer [Dragoon]    [Found in Earth Shrine]
Default command: Jump
One of my personal favorites. Strong physical abilities and great Jump command that lets you avoid damage while in the air and then attack.
Lv1    Jump    50     [Command]         Aerial attack to an enemy.
Lv2    Lance    150   [Command]         Drain attack [Hp and Mp] to enemy
Lv3    EqLanc  400  [Automatic]         Can equip Spear despite class
Total Ap needed to master class: 600

Dancer    [Found in Earth Shrine]
Default command: Dance
Fairly weak [and usually useless] characters. Can use dances to drain enemy's Hp among other things. Dances take no mp to use.
Lv1    Flirt    25      [Command]        Thwart enemy's attack
Lv2    Dance    50      [Command]         Randomly use on of four dances
Lv3    EqRibb    325    [Automatic]        Can equip Ribbon despite class
Total Ap needed to master class: 400

Chemist    [Found in Earth Shrine]
Default command: Drink
Physically weak characters that also lack magic but are still extremely useful. Mix lets them to combine two items to produce new and rare ones.
Lv1    Medicin    15      [Automatic]         Potion/Ether's effect is doubled
Lv2    Mix    30      [Command]         Mix two items to make a new one
Lv3    Drink    45      [Command]         Drink special enhancing drinks
Lv4    Recovr    135    [Command]         Recover from most status cond.
Lv5    Revive    405    [Command]         Revive fallen ally with minimal Hp
Total Ap needed to master class: 630

Mime    [Found in Submerged Wind Shrine]
Default command: Mimic
Semi-weak characters that can copy their ally's and enemy's attacks. Have three other blank command slots that you can fill.
Lv1    Mimic    999    [Command]          Copy preceeding command

reference charts:
classes ranked in order of usefullness
classes ranked in order of Ap needed to master
which classes I think you should have each characters master [In order]