After a whole night and early daylight spent, I finally came up with the final list of skills that are going to be the final skills I want to get along with the upgrades from my old skills. Of course, once I upgrade those old skills, I will not be able to use their lower-form version. I already calculated whether it is worth it to increase their cooldown time and their MP consumption.
For the swordsman class, I managed to get two new skills, two active skills, and another existing skill that is upgraded twice.
First, [Swords Dance], which is a tier 4 skill. It summons 8 swords that spin around the user and can be fired like a projectile at any enemy. If an enemy collides with the skill while they are not fired, they will inflict damage equivalent to the average damage that can be dealt by using basic attacks. And every 5 collisions, one blade will disappear. It costs 5,000 MP to cast once and has a cooldown of 10 minutes before it can be used again.