Skill system optimization
skills = new SkillType[2];
skills[0] = a; skills[1] = b; skills[2] = c;



This is simply wrong.  You make an array of size 2 and then put three things in it.  

Also, you never set a, b, or c, so you might as well leave off the second line.  


public int acost, bcost, ccost;
public int acooldown, bcooldown, ccooldown;



These are never read, so you could delete them.  

In general, this code feels incomplete.  Your enum looks about as short as it can be for the functionality.  The rest of the code is unclear about what it is doing.  You could probably delete almost all of it.