Okay @JoshRaed I think your biggest problem here is that you don't have a magic system but rather a magic mess. You have a lot of seperate elements and some do's and don'ts, but you lack any sort of fundamental rules as to why and how it all works.
So I propose something far more radical than just giving you a couple of patch notes, I am going to try and craft a magic system myself, based of the list @IndigoShirtProd has provided. it's the only way I can begin to make sense of this all.
I will be changing some stuff from that list however and there are elements I will outright remove, all in service of making a streamlined, workable magic system.
Now before I start here; It's entirely up to you to use what I provide here. If you think it sounds good, then great. Do you think it's the biggest amount of horseshit you've ever read, also great ignore everything I said. I'm not here to force you to do anything.
Aight, let's get cooking!
So for starters we need to define what are Dark, Light and Neurtral magic really? Are they 3 different sources of magic or are they expressions of the same source? You said your chosen hero can neutralise both Dark and Light magic, you also said his powers are influenced by his emotions and you mentions that Dark and Light magic are weak to one another. Further, we need to define what sets Dark magic abilites and Light magic abilities aparts from each other. So I propose the following:
- Dark and Light magic are expressions of the same source of power, but influenced by the emotions of the wielder (similar to the Force from Star Wars)
- Dark magic is fueled by the casters anger, hate etc.
- Light magic is fueled by feelings of love and compassion etc.
- Dark magic is offensive and destructive in nature.
- Light magic is defensive and creative in nature.
- Neutral magic (or maybe rename it Gray or Twilight magic to keep in line with the Dark-Light theme) is the balance between Dark and Light.
Aight, now that we defined Dark, Light and Neutral magic and decided it all comes from the same source, we need to figure out what is that source? Here I wanted to make sure the restrictions you have put in place are honored, but more importantly, I wanted to figure out a way to organically weave into the the core of the magic system your desire to summon a powerful spirit at the climax of your story. What I'm about to suggest might be a bit "out there" for you, but I think it could work. I am using Final Fantasy 7's lifestream as the blueprint here.
- The source of magic is the "soul" of the planet
- The soul of the planet is composed of the souls of deceased humans and animals.
- When a being dies, their soul returns to the planet.
- When a person is born, however, they receive a piece of the "soul" of the planet.
Now how does this tie into the spirit?
- The spirit is the soul of a deceased being or even that of the planet itself!
- The being can be anything, an ancient person, a primordial animal or even some semi-divine creature.
Aight, so now that we difined the schools of magic and its source, we need to figure out how one is to wield such magic. You mentioned sorcerers and circle magic, but leave the mechanics kinda vague. You also say that magic has to be "imbued" into a person by a sorcerer to make them magical, but this is something I am going to delete from the system. You do seem to make a distinction between people who need and don't need circle magic and this gave me the idea to make two distinct types of magic wielder:
- Sorcerers, extremely rare and powerful people who can wield magic without help (the Dark Lord, the Light King, maybe their top generals, and definitely the Chosen hero but maybe he doens't know he's a sorcerer at first.)
- Circle mages, everyone else. People who can only cast magic using elaborate glyphs.
Before we delve deeper into each type of magic wielder, we need to further define how magic is used and how it works and what its limitations are. I had the following idea in mind.
- Because the source of magic is the "soul" of the planet, magic is the manipulation of the elements of the planet (not like avatar)
- Magic can only be cast outward, as in, a magic wielder can never use magic on themselves. This limits teleportation, healing of self and flight etc.
- Magic can not manipulate other being with a soul (this is a variation of what @lizardlullabye proposed), this means you cannot heal the bodies of other people or even animals. But you can hurls rocks at them or shoot lighting bolts at them etc.
Okay, now let's dive deeper into sorcerers and circle mages.
First up sorcerers:
- As mentioned before sorcerers are extremely rare and powerful.
- Then can channel the magic without aid, through their own body to manipulate the planet.
- Because they channel magic through themselves, the magic is "colored" by their unique emotions, creating either Dark or Light magic
- This means a sorcerer is always either a Dark mage or a Light mage, they relly on their emotions to use magic.
- Sorcerers can use Circle magic, but are maybe too proud/arrogant to do see.
Next up, circle mages. For Them I really wanted to better define the use of the spellbook and what exactly these "circles" are . You are kinda vague on that front so I once again defined it on my own. For this I take inspiration from series like the Owl House's Glyph magic and Fullmetal Alchemist's transmutation circles. I decided to combine that with a trope used in a lot of fantasy worlds, were magic is a sort of mastery over and ancient or primordial language. I also wanted to keep your idea of spells being combinable and adjustable So here is what I I got:
- Circle mages need to use elaborate runic symbols to cast their magic.
- These runes are the true language of the planet, and form ancient words or phrases.
- Runes can be combined into new words or phrases, but need to make "sense" in the grammatical rules of the language.
- Circle magic is always neutral, because it doesn't channel magical energy through the caster. In a sense, Circle magic is asking or talking to the planet itself and requesting it to perform a deed for the caster. No emotion is involved.
- The book of spells is a collection of words and phrases in the language of the planet. Essentially a sort of dictionnary.
- The spirit summon can only be done by cirlce magic! The caster(s) are essentially asking the planet to send a massive amount of energy to their aid.
I thkn that's about it. I'll admit it's a bit rough and probably needs some refinement and tweaking, maybe some changes to function within your story. But this was honestly the only way I felt I could make sense of the various elements you have right now.
And again, if you think it's bullshit and don't want to use this, you don't have to. I know I have proposed some radical changes to your system and likely your world with this. But even if you choose not to use any of what I have said here, I want you to have at least one big take away from all this:
Start with the fundamentals of your system first. What is is? Where does it come from? How is it used? before you start heaping on abilities, rules and exceptions on the pile. You need to understand the basics first before you can build further.