To reach the skill cap, you'd need to equip 3 Vitality Jewels into your armour, or combine a piece of armour with Health Boost Level 2 on it with a single Vitality Jewel which would add one extra level, up to the cap, which is Health Boost 3.
I.E Health Boost, requires Vitality Jewels, which are size 1 decorations that provide a single point towards the skill. If you need more levels in that skill (up to the skill cap, which is different per skill) then you either have to find and slot in more of the same decoration, or find armour pieces with the skill already on it.
Originally posted by Greb:Decorations? They provide 1 level in the specific skill.