XP

XP, EXP or experience its the only form to level up. When you raise a new level, you gain 5 points for stats and 1 skill point for level up one of your skills.
 * 1) 3000 XP
 * 2) 5000 XP
 * 3) 8000 XP
 * 4) 10000 XP
 * 5) 13000 XP
 * 6) 15000 XP
 * 7) 19000 XP

Trivia
XP its an emoticone in many places and social media like twitter