So, life magic is incorrectly named. It's D-particle (magic particle) manipulation magic. Basically raw magic into specific forms. As for how magic works for a typical person, magic is divided into different categories (enhancement, attack, analysis, life, healing, etc.) and you have a level for that categories and a talent(how fast level increases) for it. This can all be seen through status or analysis magic (girl at the end has a good talent rank for analysis magic and checked the teachers talent rank for life magic).
Now, how they learn magic is that the stare at the magics magic circle (really, they don't think about or dissect it, they just stare) and after a period of time based on their talent rank, they will just learn the spell. Someone who knows the spell can copy the circle and distribute it for learning. Commonly used spells appear more in dungeons (new spells are rare).
Now, the exception. There are sages who can just create new spells and distribute them. I think there's only, like, 11 or 12 people who can do this. The reason life magic is like this and has these spells is because the last sage of this categorie of magic only figured out how to use it for utility. That doesn't mean they weren't clever, they figured out how to use it to process materials made of d-particles along with other spells to assist in the processing, but they didn't come up with a way for those spells to keep up with the attack scaling of attack magic. Attack magic starts with 'bullet' spells which, at level 0, is about as strong as a gun. The same spell will hit harder as the user levels attack magic, which doesn't happen with the utility spells of life magic. In fact, all other categories have their spells improve directly as you level the category but life magic just lets you use more of the same spell concurrently. Mc figures out that he could get more force out of them by layering them on top of each other and having them all move in the same direction, making it comparable.
So, when mc becomes the next life sage, that's when creativity comes into play. He'll start rearranging the d-particle planes into stackable shapes like hollow blades, hollow cones, or hollow half spheres(this one is more effective for applying element like effects).