That's what I meant by the something else.
The fact of the matter is, though, that if you for something like, say, runes, you will have to specialise to do anything other than dabble in them, as each carving/drawing/painting/etc. has to be very precise, otherwise you end up like me.
And about that worst thing that could happen, well...
Actually, you really don't want to know.
There's nothing wrong with doing a little dabbling to start with (so long as you don't get involved with any of the magic that automagically locks you out out others permanently), though I do agree that a mage has to eventually specialize if they want to be very good at anything.
For one, it's a matter of the sheer amount of practice you need to put in. For mortal martial arts, you'll never be a master if all you know is the basics of several different styles, so too is it with the magical arts. With the amount of time and effort I've put into Rune Scribing so far, I could nearly have a mortal medical degree by now (or actually I could have several if you count the time I've spent in timeless planes of existence). And I'm still nowhere near mastery of the art.
Then there's the fact that, to get really good at a magical art, you need to be mentally devoted to it. If you ever come across a highly-focused master pyromancer, you'll quickly learn they can do things with fire magic that other mages couldn't even dream of, and that's partially because they've spent so much time practicing with it, but also because they've tuned their minds to fire, so that it's as intuitive as breathing to them. When you get that focused on a magical art, it's not know for sure if that practitioner becomes unable to cast other kinds of magic, if they're simply mentally adverse to it, or if those two conditions are basically the same thing.
Of course, there's no need for you to get that highly-focused on a single art. If you wanted to do fire magic, for example, but also work with other elements, you could become an Elementalist. Or you could pair it with a completely different altogether, like, illusions or necromancy. You won't be able to do the same things as a highly-focused practitioner, but you gain more breadth to your abilities and might be able to unlock some synergistic uses or powers. And there's a lot of breadth and narrowness to the various arts, which can be mixed-and-matched at various levels of focus, and you're not really even limited to any sort of traditional schools of magic, as my friend Kimber the Ailuromancer can attest.
Ah, your ignorance shines through. There's a reason stereotypes and specialists exist: magic comes from the mind, and familiar, traditional images help it channel magic. Witches don't dress in orange leopards because it isn't conducive to their casting. This is also why you spend time preparing your materials, to have a better mental image of them.
And the worst thing that could have happened is opening a crack in the defenses of this plane, letting demonic armies breach through. Then, the legions of Celestia would have to march in our defense, turning the mortal plane into endless battlefield.
This is why you stay in school. Take an apprenticeship. It's worth it.
I will agree with you on why the traditional stereotypes and specialists exist, i.e., mental focus, but I don't agree that that means we need to keep to the tradition always, as different mental images are also useful. I wouldn't have been able to survive on the Hyperplanes of Traaldagur for three weeks in robes and a pointy hat instead of my akubra and duster, and it's not just because of the protective magic woven into them. All those times I should have died, the sheer image of them gave my magic a survivalist edge, so that my gameseeker bullets, for example, always flew true. And, besides for showing off, I will admit that the image of robes is very useful for rituals (I can't imagine how armored mages do them, frankly).
And I do agree that Fniff should try to seek proper magical training. There's a very good fae school that can be reached through Tara, if he can make it there. (There's other ways to the Fae Realm, but it's best to go through Tara if he can, since it will bring him closest to the place and he won't have to travel through the Fae Realm forests and deal with their time-warping properties).
Just out of curiosity, are there any other arcane artists who prefer to study fine art of illusions and bending minds of others into your will?
I've tried illusions a few times and found them useful, but they're a little hard for me since a) I Magelocks tend to make a lot of noise when you use them, and B) you can't really change a spell up when you cast it with a Magelock, either before or after it's been cast.