My Summons (Notes)

Chocobo
Bomb
Shiva
Ifrit
Ramuh
Carbuncle
Golem
Astaroth
Titan
Ruby Dragon
Syldra
Magic Pot
Asura
Malboro
Ark
Ahriman
Zone Seek
Phoenix
Odin
Atomos
Leviathan
Typhon
Bahamut
Ultima
Tier 1 = 1-1500 Damage | Less Importance | MP Cost(1-25)
Tier 2 = 1500-4000 Damage | Medium Importance | MP Cost(25-50)
Tier 3 = 4000-9999 Damage | Greater Importance | MP Cost(50-255)

Tier 1: Chocobo, Bomb, Shiva, Ifrit, Ramuh.
Tier 2: Carbuncle, Golem, Astaroth, Titan, Ruby Dragon, Syldra, Malboro, Ark, Zone Seek, Ahriman.
Tier 3: Asura, Magic Pot, Phoenix, Odin, Atomos, Leviathan, Typhon, Bahamut, Ultima.

Similar or Successor.
Shiva< Titan (No Ice Type Sucessor, closest is Titan)
Ifrit< Ruby Dragon (Fire)
Ramuh< Syldra (Lighting)

Astaroth< Asura (Healing)
Ahriman< Odin/Atomos (Instant Death/Demi)
Ark< Bahamut (Non-elemental)