I've been having trouble figuring out how the knowledge points work.
Knowledge Points (also commonly called KP) only apply to the current class you are playing. Each class has its own unique build of knowledge points, and each class can be distributed in different ways.
So in short, Knowledge points are not connected between multiple classes.
The things that ARE share between classes are:
1) Racial/Common Skills.
Racial and Common Skills are shared in classes of the same tree. For example, A Hunter, Engineer, and Ranger all share the same Racial
Skills, but each class also has their own Class
skills unique to that class.
You cant use Hunter Class
skills on a Engineer
You cant use Hunter Racial
skills in a Thief.
2) Class Certificates
You can use any class certificate on any class. You can
use a Hunter Certificate on a Thief class. There are many certificate combinations which require you to use certificates form different classes.
3) Class Expertise
Class expertise is share between all classes. The more classes you level, the higher your class expertise bonus will be. This increases your HP, MP, Healing, Attack, and M-Attack bonuses on all your classes.
You can "wield" any weapon on any class, however some classes have skills which require certain weapon to use those skills. Some classes are more flexible however. For example, a Warrior only needs a 2-Handed weapon for some skills. While Warrior's are designed to use an axe, they can use other 2-handed weapons such as a Katana, or Greatsword.