Just an idea
Easy quests - 3 points
Medium quests - 6 points
Hard quests - 9 points
Option:
Comments and ranking game - 1 point
As the system required, oriented more towards on quests than comments and ranking games, but even that does not underestimate the component, so you get two in one
This is a proposal for a new player rankings
Serf - Pikeman - Halberdier
Archer - Marksman - Rouge
Footman - Swordsman - Squire
Crusader - Knight - Paladin
Cavalry - Champion - Master