How to Spend Skill Points Edit
First, make sure you're not in any GUI.
Next, Press K
The inclusion of an ability tree is quite a recent event. Basically every time you level up, you will get 5 points to put into stats, and 1 skill point. This skill point can be used by putting it into one of the many abilities in the ability tree. This will either unlock a new ability for you to use, or upgrade the ability.
For damaging abilities, putting more skill points into them will do one of these two things: either increase the damage it deals, or if it's an ability that produces numerous projectiles, example "Charged Bolts", it will add extra projectiles to the spell.
For non-damaging abilities, putting more skill points into them increase the main effect of the skill (See: Leap.)
For Leap (and Whirlwind), putting skill points into it will increase the size of the leap.
For Teleport, Torch shot, and Ladder shot, skill points have no function.
Most Efficient Way to Spend Skill PointsEdit
The most efficient way to spend skill points, as of now, is to focus on one ability, and invest all your points into that ability. This is because the more points put into an ability, the stronger it becomes, so spreading out your skill points amongst many abilities is not viable. However, for abilities such as "Shockwave" and "Flame Breath" which you don't get until later levels, you would need to put your points into other abilities first.
Influences on the GameEdit
Having an ability tree and the way the system works means that you no longer have to invest all your stat points into offensive stats and run pure glass-cannon builds. This means that people will be able to commit to building more tanky, especially for the late game.
Also, now that characters no longer have to rely on stat points to ramp up their damage as they can do that with skill points, and due to the changes to how defense works, Fortitude will become a more important stat, especially for the late-game. This means that warriors, in comparison to the other classes, will then have a much stronger late-game when defense is worth nothingm and mobs are hitting you for full damage, as Fortitude gives warriors the most amount of health out of all the classes.