According to the treasure table, here's how Lucky Charm works.

At Lucky Charm 1, the character has a 2% chance at finding 1 Common item of these types:
  • Scroll, 25% of the time
  • Arrow, 30%
  • Gold, 30%
  • Precious, 15%
At Lucky Charm 2, the character has a 3% chance at finding 1 Common item of these types:
  • Scroll, 25% of the time
  • Arrow, 25%
  • T_ST_SecGearNormal, 25%
  • Precious, 25%
At Lucky Charm 3, the character has a 4% chance at finding 1 Common item of these types:
  • Scroll, 20% of the time
  • Arrow, 20%
  • T_ST_SecGearNormal, 20%
  • T_ST_ArmorNormal, 20%
  • Precious, 20%
At Lucky Charm 4, the character has a 6% chance at finding 1 Common item of these types:
  • Scroll, 20% of the time
  • Arrow, 20%
  • T_ST_SecGearNormal, 20%
  • T_ST_ArmorNormal, 20%
  • T_ST_WeaponNormal, 20%
  • Precious, 20%
At Lucky Charm 5, the character has a 7% chance at finding 1 Common or Magic item of these types:
  • Scroll, 10% of the time
  • Arrow, 10%
  • T_ST_SecGearNormal, 10%
  • T_ST_ArmorNormal, 10%
  • T_ST_WeaponNormal, 10%
  • GoldBig, 10%
  • T_ST_SecGearMagic, 10%
  • T_ST_ArmorMagic, 10%
  • T_ST_WeaponMagic, 10%
  • Precious, 10%
At Lucky Charm 6, the character has a 8% chance at finding 1 Common or Magic item of these types:
  • Scroll, 15% of the time
  • Arrow, 15%
  • T_ST_SecGearNormal, 10%
  • T_ST_ArmorNormal, 10%
  • T_ST_WeaponNormal, 10%
  • GoldBig, 15%
  • T_ST_SecGearMagic, 5%
  • T_ST_ArmorMagic, 5%
  • T_ST_WeaponMagic, 5%
  • Precious, 10%