An Overview of Magic

Beginning Brain-Wiggles
I have discovered that, in my world, the magic number is three. This is only partly because there was a kick-ass Dark Crystal Art Book with all kinds of law stating that three was the most stable number, and was thus the number of magic (with other, forbidden numbers too). The rest of the reason is total coincidence.

Magic Itself
There are three main "classes" of magic, in as much as mortal minds can comprehend. The higher beings such as angels, seem to enjoy magic of their own which does not fit with this system. It is however, useful to bend the simple geometry of the human mind around and against such mystical forces.

1 - Hedge Magic
The simplest kind, which most anyone can master, given time, knowledge, and resources. The magic for the most part is bound in the objects, though bond is a very loose and mostly incorrect way to put it. It is the passive magic of things; the way the deck of cards can be used to predict the future, the way that a bowl of water can reveal visions; how, with the right chalk marks, a mirror can hold things inside its reflections.

2 - Theurgy
The classical magic, where words and spells summon powerful effects and rain destruction down from on high! Difficult to learn, even for those that devote themselves to it. Works pretty much like in regular DnD, probably only wizards can learn this kind of magic easily (but that's a discussion for another day). 

3 - Arcana
This is deep wizard knowledge man. This is where the whole "sufficiently advanced..." and "appears to be magic," stuff kicks in. This is where being able to enter into contracts with outer-powers comes in, where you can find the ways to the Undying Lands of the Fae, where you can discern the routes to eternal life. Its magic to everyone else, to the sufficiently learned, its just elementary.

Magic Items
Similarly, there are three kinds of magic item, which roughly sort of map to the three kinds of magic.

1 - Awoken Items
All things have their spirits, and the spirits of made-things are strange indeed. Unsure of what they really are, they sleep, and have little magics of their own. It takes great deeds to rouse them to greatness again. This is how the fighter can ambiently make magic weapons, how the cloaks of invisibility get made, how Magic Mirrors get to answering questions about subjective opinions.
Coincidently, this type of magic item has the greatest abundance of sentient items by far, even if the sentience is only the passive type.

2 - Enchanted Items
These are your classic "A WIZARD DID IT" items. They have magic woven into them, the item is more of a store and a repository, than a source. They will run dry and disenchant naturally if you let them, but many items (especially those made by competent wizards) have ways to replenish their enchantments.

3 - 'Magical' Items
This type of magic only sort of counts, these are the items made of magical things, and thus possess their properties. Healing potions, adamantine weapons, mithril armour, that kind of thing.

How this fits into the game
Firstly, I imagine Wizards interacting with the types of magic like a ladder.
They start off with very few spells, but the ever usable (but minor) Hedge Magics.
As they level up early and into mid levels, they begin to amass their vast repertoires of spells that they are famous for. Then, as they progress, they slowly pick up Arcana, and puzzle out the deeper mysteries.

What about other magic classes?
I really don't know.
I do like the difference between Wizards and Sorcerers being learned versus innate, but that doesn't jive nicely with my magic system. And I don't know what the third type of wizard would be for the "Magical Trifecta".
I could on the other hand, try and wrangle out classes that each focus on other types of magic. For example, if Wizards overall focus on Theurgy, then you could have a Hedge Wizard type class. An idea I had for a type of magic user who focused more on Arcana would be a kind of Monk type character who pondered the universe, but then I lose out on the space for a Sorcerer.
Oh I don't know what to do.

Also, the Awoken Items are a great way for non-magical folks to get/make magical items, which is always a good thing I think.