I just won't give people a huge amount of mana. Also thinking about how heavily I want genetics to play into it. Maybe only certain families use fire spells because only they have access to that kind of energy. ?
Just limiting how much mana you give people doesn't really work, the issue is that even low-level magic can be too useful and take over every aspect of how people do things. It's such a multitool that it becomes boring and disingenuous, the solution to every minor problem, it will eat up any other more interesting form of problem solving. And any character that you give more mana, will just be that much worse to handle, and you'll end up in a situation where they're too powerful and there's just too much that it's possible for them to do that the only way to nerf them is make them stupid and miss easy solutions, and readers hate that because it's not satisfying.
Oh also this magic system would completely gatekeep people with aphantasia, aka no internal visualization. Not necessarily a bad thing if you're already limiting who can use magic, but something to keep in mind. Could also be a plot point, someone who 'should' be able to use magic due to bloodline or whatever, but can't.
It's also important to understand why each part of the process is necessary, what's the fundamental reason that each part works the way it does? Why would an fundamental piece of reality be affected by speech? Is it truly necessary, does it truly make sense? I'm not saying you can't or shouldn't do it, I'm saying you should ask yourself if it makes sense why it works the way it does, and if not, either change it or go deeper to make it make sense, so your world-building has a stronger foundation.
In my system, there's an underlying force separate to mana that affects and shapes it and allows for things like intent to work on it. Allows for a manipulator of magic to do more than shape it manually (the difference between manually using life magic to weave and generate specific types of flesh to heal someone, versus directing magic at someone and telling it to heal them). It's the very concept of, well, concepts. Meaning itself (or, well, it's not important to the discussion, but that's not all it is, it's more like, connections between things, like, karma. Meaning is just a facet of it's application). Unified and originating from the being that created existence, whom a part of resides at the core of every soul, which is what allows people to access it's power and unifies what meaning
is. That lore isn't necessarily important for the story itself, what
is is that the way it works has implications. The spoken word is merely one vessel for meaning, but there's also writing, music, painting, sculpture, dance, and all of these things can carry meaning, and thus shape magic. Word is the most common just because it's so specific, but anything that can convey meaning can work.
However, I also limited who can use it, and how much. A person can only use a concept that they have formed a significant connection to, though the barrier to entry is lowered by the user's power (someone who is capable of influencing the world around them more, has a higher karmic 'weight' to them, and thus have an easier time imposing their will, intent, and drawing on concepts. Note this doesn't just mean raw magical power, political and economic power counts too). Going back to the healing example, only someone who has truly enveloped themselves in what it means to heal, or is so capable of healing that they have an inherent authority over it, can just invoke the concept of healing and let it happen. If just anybody can use any concept, then magic becomes way too flexible and eliminates challenges, and thus conflict. And stories are all about conflict and overcoming challenges, so making magic too flexible hurts your ability to tell a story. If the common mage can wave and hand and the person is healed, then injuries stop mattering, but if healing can only be done slowly, by those who are extremely well trained (like to the level of a real world doctor/surgeon), then all of a sudden it
matters when someone gets hurt.
...I like nerding out over my magic system don't judge me