There exist two types of skills the first type are the common ones and even those common ones are divided by their rarity.
The rarity of those skills is divided by the scale from 1 to 10, with 10 as the rarest.
For example, those two are the most common ones that every human get from the beginning (Rarity:1).
Appraisal(A skill that can show the stats of other peoples and monsters, and can also show the information of equipment and items.)(It can only show the name, Age, level, and Job)(Every human has got this skill from the beginning.)
Item box(A skill that provides the user with 100 slots. And those slots can store different things also each slot can contain up to 100 things as long as they are the same.)
(This was also a skill that every human has got this skill from the beginning.)
Other skills examples with different rarity.
Enchantment(Rarity:4)(A skill that doubles the power and speed of the user for 1000 magic power every minute.)
(This was a usual skill that a lot has got it from the start. Even though not everyone can get a skill, and the rarity of the skills change from one another.)
Storage(Rarity:5)(As it names apply this skill allow the user to have infinite storage.)
Teleport(Rarity:10)(A skill that allows the user to teleport immediately to any place that was visited before.)
Construct(Rarity:6)(Allows the user to construct anything as long as there are materials.)
Magical Eye(Rarity:9)(A skill that is a higher version of Appraisal that shows all the stats even their skills and magic.)
Sword skill(Rarity:2).
Dual Sword skill(Rarity:3).
Martial Arts(Rarity:4).
Skills can be obtained by training like Martial Arts or sword skills or can also be obtained by killing high-level monsters (Rarely) or by opening scrolls.
And the other type of skills are the unique skills which only a small number of people can obtain. And since it is unique two people can't obtain the same unique skill.
The unique skill of our MC.
Skill looter(unique skill)(A skill that makes the user takes the skills and magic from the monsters or humans he kills.)