Skills with max level of 1/2/3 require spending 1/2/3 additional skill points to become active without a skill slot.

For NG+. Skills with max level of 1/2/3 require spending 2/4/6 additional skill points to become active without a skill slot.

Skills with max level of 1/2/3 require spending 0/1/2 additional skill points to become active without a skill slot (Perk already always active with these value).