Never tried a 4-tier system myself. I’ll give it a bit of a shot.
FIRST STAGE
Mage (Anima)
Promotes to Spellblade and Sage
SECOND STAGE
Spellblade (Sword, Anima)
Promotes to Dark Knight and Crusader
Sage (Anima, Staff)
Promotes to Sorcerer and Strategist
THIRD STAGE
Dark Knight (Sword, Anima, Dark, Cavalry)
Promotes to Nephilim
Crusader (Sword, Anima, Light, Armoured)
Promotes to Purifier
Sorcerer (Anima, Dark, Staff)
Promotes to Dracomage
Strategist (Anima, Light, Staff, Cavalry)
Promotes to Valkyrie
FOURTH STAGE
Nephilim (Sword, Axe, Anima, Dark, Cavalry)
Purifier (Sword, Lance, Anima, Light, Armoured)
Dracomage (Anima, Dark, Staff, Flying, Dragon)
Valkyrie (Anima, Light, Staff, Flying, Cavalry)