Wow Rogue- Combo Points

Either set up combo points as a status value or use object variables on the combatant for that. Status value is probably the better way if that's used as use costs for other abilities.

Receiving them for use of abilities would just be setting that up as either use costs or user changes (i.e. status changes) in your ability. That way, using the ability will gain the user those points.
Using them in other abilities is just use costs like e.g. MP.