Geralt's strength growth from equipment is fairly straightforward: the higher his level the higher the level of the equipment he can wear, and higher level equipment has better statistics. So to understand this you also need to understand the Equipment, Abilities and Mutagens that fuel it. Witcher 3's character development is almost entirely based on an unlock-by-level system the higher your level, the higher the level (and therefore stats) of the equipment that you can wear and the more skill slots you unlock, on top of the additional skillpoint per level. Unlike many games, however, gaining levels doesn't give very many character stat benefits by itself. Like many RPG games, The Witcher 3: Wild Hunt has extensive character development and levels.
