When you first start, you will need to kill 150 NPCs. After reaching 150, you have completed your ELO for the day, and gain a 1% stat multiplier. The kills reset 24 hours after they are finished, with no relation to server time. If you finished your kills at noon on Monday, then your kill count will reset at noon on Tuesday. You can only complete the ELO kill count once per each 24-hour cooldown. You can also purchase ELO boosters from the Store that will grant you 5% (0.05) ELO when you consume them.
ELO plays an extremely large role in increasing a player's stats and damage. It works as a stat multiplier for all of the gear you equip.
Example: If you have the Staff of Awakening equipped with 100% ELO. The base Magic Attack bonus would be increased from 17,500 to 35,000 and the Mage Strength bonus would increase from 42,114 to 84,228. This effect does not increase the luck or the drop rate bonus of the weapon or equipment. However, this works with all equipable slots in the game.