In players can gain skill points by leveling up with XP and by completing Region Progress tiers. The quickest way to gain levels and earn skill points is by completing quests on higher-difficulty World Tiers.
While killing bosses is a great way to farm loot, it isn't as efficient for gaining the XP needed to get skill points. Every level rewards one skill point.
Not every class will be available to play in either the Early Access Beta or the Open Beta, but the three included in early access, Rogue, Barbarian, and Sorceress, all level at relatively the same speed.
However, AoE attacks will help players to gain XP faster than more targeted attacks just through the quantity of kills. Killing can also give side quests, creating more potential XP income.Read more on screenrant.com