I'd also like some help with the gods of the world, specifically their domains. Domains without opposites (Animals, for example) are preferred but not required (Harvest is possible) but strong, universe-binding domains with opposites (such as Chaos and Order) are definitely out.
EDIT: There's also Divine magic which is derived from the gods' domains. The gods' domains should be something other than Life, Death, or Elemental.
Well, what's the point of gods? Just adding additional spell types?
If so, I'd obviously lean towards gaps left behind by the current trio; depending on how you want the world/system to work, you might want the opposite. That said, assuming Life/Death/Elemental has those areas covered and needn't be repeated, we're probably mainly left with more esoteric forces and concepts, like Emotion (or specific emotions), Gravity, Time, Tides, Erosion, and so on, as well as any gaps left behind by the main three, like Earth, Metals, Ash, Water if that's not under Frost, Plants or Growth if they're not under Life, and so on.
Another way to get domains, or at least be inspired to find domains, is to look at what you've got already and see how they fit together. For instance, combine Life and Death. What does that give you? Anything? Regrowth, Cycles, Equivalence, something like that? Might make for good domains, might not. Try again with Death and Elemental, wonder if Death+Lightning is any different from Death+Fire, and so on.
As for magic, there are three types:
Life
Death
Elemental - Fire, Frost, and Lightning
What I need help with is in making magic that's available to all types of mages such as Enchanting.
Meaning what? Broad ideas like "alchemy" or "cabalism," or actually making Enchanting a functional, balanced set of concrete values?
A word other than 'type' to describe the three...types of magic would be great.
Sphere, Domain, Valence, Arc, Path, Sigil, Veil. Made up words like Ukmak or Pel could also work.
Trying to figure out a bonus to give when someone reaches Adept at casting a fireball. On a d10, it'll give the player +2 to teaching the technique to others, but what else should it give?
This is likewise hard to answer without context, but is there anything neat a spell could do for a player at that point? Heal them, stun enemies, become AoE, reroll 1s, ideally leaning towards "this is an extra effect I don't have difficulty remembering or applying" and away from "this is more numbers and they're awkward to do?" Limiting it to crits or high rolls (or low rolls, as mentioned) could help with both that and keeping it from becoming too powerful.
I was just thinking of making a magic girl type game. It'd probably have a focus on teaming up with bonuses for having relationships with other MGs.
The setting would probably decide what the main focus would be. The main ideas being a pirate themed one that is lower powered but with more bonuses for friends and items, an urban fantasy that's more about fighting other evil MGs, and then finally a sort of Sci Fi setting that has a lot of mook slaughtering and villain of the week type stuff.
Friendship Power Pirates sounds hilarious. I notice you specify
other evil MGs in Urban Evildoers, which is either a prophetic typo or thinking ahead.