The fighter has a +2 attack and defense, but magic is not doubled. In other words,the number on the card is how much damage it does.
The white mage can change any defense cards. -1 attack but +3 magic(after it's doubled).
The black mage can change any attack cards. -1 defense but +3 magic(after it's doubled).
The red mage can change any attach cards. -1 attack and defense but +3 magic(after it's doubled).
The thief can steal from decks or hands.-1 defense and -2 magic.
The gambler can pick up 4 cards per turn. When attacking, flip a coin to determine whether the attack works or not.
The summoner can remove monsters from the field but can't attach when he places a monster on the field.
The illusionist doesn't need suits(except for monsters). In others words, a magic can be used as a defense and so on. He gets -2 to all stats.
The guardian can choose the monster who takes the hits. He gets +3 defense and +2 magic but -3 offense.
The ninja can attack through defenses. In other words, an Ace of hearts and 2 of diamonds beat a King of hearts and 10 of diamonds because a Ace beats a King. Gets +3 to attack and +2 to magic but -3 to defense.
The geomancer gets a +2 defense and a +2 magic when one monster is on the field, +1 defense and +1 attack when two monsters are on the field and -2 magic and +2 attack when the field is full of monsters.
The scholar gets a -2 penalty to all stats but can reveal 1 card each turn.
The shaman can attack two monsters at once but has to sacrifice 1 card to attack (even normally).
The prince gets a +2 bonus to all stats but starts with 5 cards.
The knight gets a +3 defense but magic=4
The samurai gets a +3 attack but magic=4
The stalker can hide his cards unless he attacks but gets a -2 penalty to everything.
The bard can paralyze the enemy he attacks but gets a -1 to all stats.
The monk cancels any stat bonus and reduces it to zero but gets -2 to defense and attack.
The priest can revive a monster by sacrificing 3 cards but gets -1 to all stats.
The apprentice can copy any special ability but gets -3 to all stats.
All graphics are from FF3 NES VERSION