An Explanation
Cure Potency refers to the effectiveness of healing spells, such as Cure and Curaga, and even spells like Healing Breeze wielded by a Blue Mage despite not bearing "Cure" in their names. Anything that increases Cure Potency directly affects the amount of HP healed by these spells. It should be noted that Cure Potency does not increase the healing effects of Job Abilities, such as Chakra or Curing Waltz.
An example: A White Mage casts Cure II which normally heals their target for 90 HP. If they equip something that gives them Cure Potency +10%, their Cure II will heal their target for 99 HP.
Cure Potency ignores the "soft caps" of healing spells. Equipment that enhances Cure Potency is usually much more effective for healing purposes, as opposed to equipment that enhances Healing Skill or Mind which are greatly limited by soft caps.
Cure Potency only applies when Cure is used to heal a target. It has no effect on the damage done by Cure when used to attack Undead enemies.
The highest possible Cure Potency you can achieve with gear alone is +42% with Asklepios and Templar Mace via Dual Wield, Aristocrat's Coat, Medicine Ring and Roundel Earring. With the Healing Feather enchantment, you can have another 15% for a total of +57%, combined with a Divine Seal, you can reach a maximum of +157%. Meaning if you use Cure V for 800 HP, you could get up to 2056 HP out of it. Take into account that the Medicine Ring will only trigger if your HP ≤ 75%, and your TP ≤ 100%.
You can achieve higher Cure Potency during Besieged with the Volunteer's Khud, which grants an additional +5% potency. Also during Salvage you can equip the Lambda Sash for an additional +3% potency.
Equipment that Enhances Cure Potency
Level Type Name Potency % 29 Staff Melampus Staff Cure Potency +3% 40 Club Dia Wand Cure Potency +1% 43 Staff Ceres Spica Cure Potency +6% 50 Ring Medicine Ring Latent Effect: Cure Potency +10% 51 Staff Light Staff Cure Potency +10% 51 Staff Apollo's Staff Cure Potency +10% 52 Leg Armor Puppetry Churidars Automaton: Cure Potency +5% 54 Earring Hospitaler Earring Cure Potency +5% 55 Staff Healing Staff Cure Potency +10% 55 Staff Dryad Staff Cure Potency +10% 59 Body Restorer Cloak Cure Potency +3% 61 Throwing Healing Feather Cure Potency +15% 62 Club Asklepios Cure Potency +5% 68 Body Armor Noble's Tunic Cure Potency +10% 68 Body Armor Aristocrat's Coat Cure Potency +12% 70 Head Volunteer's Khud Besieged: Cure Potency +5% 71 Club Templar Mace Cure Potency +10% 73 Earring Roundel Earring Cure Potency +5% 75 Waist Lambda Sash Salvage: Cure Potency +3%
Job Abilities that Enhance Cure Potency
Level Job Ability Potency % 15 White Mage Divine Seal Doubles Cure Potency for a single cast (+100% plus any amount of Cure Potency equipment already being used)
55 Scholar Rapture Increases next White Magic spell potency (including Cure) by +50%.