Wizard: Start with Biological Transformation to Grind Experience

Lynch crosses over to the Wizard World and becomes a Wizard Apprentice specializing in Biological Transformation, armed with a Skill Level system.

Thus...

He equips a lizard with bat wings, transforming it into a ferocious yet adorable Dragon Attribute creature.

He transplants gastric mucosa to the Cannibal Flower to enhance its digestive system.

He equips the Poisonous Mushroom with a mouthpiece, transforming it into a Little Spraying Mushroom.

Transplanting eyeballs, modifying organs, adding limbs...

From a little wizard, he hustles his way to becoming the master of the world, starting from the transformation of low-level Magic Plants until he creates an Angel.