(T>B) Pony magic basics

My entry in this thread, https://www.fimfiction.net/group/50/the-writers-group/thread/147083/discussion-non-unicorn-magic although it includes unicorns as well.

First off, I'll cover the magic common to all ponies, regardless of tribe. Their whole bodies are permeated with it, making them one of the most magical races on the planet that are technically capable of living without it. This passive magic has a range of useful effects:

• Buffering their internal organs against impacts (bones are more vulnerable though)
• Substantially boosting their healing rate
• Eroding unicorn magic cast on them over time (this can be a good or bad thing)
• Giving their hair such vivid colours
• Allowing for manipulation of their manes and tails in various useful ways (called "capillurgy")
• Allowing their hooves to not only stick to flat surfaces, but also (with training) manipulate objects quite finely at touch range
• And of course, the big one - manifesting their cutie mark (a constant magical projection - hairs cut from it are the pony's natural coat colour) when they find their talent.

General principles
Pony magic is a sub-flavour of magic in general, with each tribe and even each individual having subtly different shades. A pony's magical capablilty rests on three "pillars" - their raw power, which is mostly fixed at an early age, their talent, which is totally beyond their control, and their experience/education. (Now, who do we know who gets top marks in all three?) Powerful ponies also tend to have longer natural lifespans, although overusing magic past their limits can invert that.

Now as for more specifics:

Unicorns
Actively utilize magic through their horns (although instinctive manifestations are possible, especially in children). Telekinesis comes to them as naturally as handwriting would to humans if we were born with written language, as do spells closely related to their talent - anything else requires deciphering complex patterns on par with a mix of sheet music and mathematical formulas, and without a close enough talent (or a magic talent like Twilight's) may be impossible anyway. So most unicorns know a few tricks well and maybe some petty utility spells. (Even TK alone can be surprisingly handy, though - and sometimes they forget the thousand ways other ponies lack it.)

Pegasi
Channel magic through their whole bodies, especially their wings. Flight in particular is instinctive, although more than getting off the ground requires athletic training/talent. At high speeds, pegasus magic accumulates around them forming a visible shield against the acceleration as well as an obvious contrail. Weather manipulation is probably their most active and intellectual power, but doing it on any scale still requires the use of one's body as much as one's head - gifted cripples are relegated to detail work in weather factories.

Earth ponies
The vaguest described in canon, it's not clear if they even have a universal power - it might vary depending on the land they're raised in or something. Still, the most common gift of theirs's alluded to is botanomancy - both passively enhancing the growth of plants by their very presence and more actively shaping them to form wonders like the old Ponyville library. (My headcanon makes this a double-edged sword though - land used to their magic will not be fertile again without it, at least for many years, and pushing plants too hard too fast will kill them.) Some earth ponies seem to eschew this gift in favour of manipulating the less organic fruits of the land - rocks, minerals and even jewels. And they are also highly represented in technically cross-tribal fields like cappilurgy and beastspeaking - although that might partly be down to me giving them a larger population.

Alicorns
Take all of the above and triple it - as your starting point. (That said, a new alicorn does take time to grow into their powers - and even they have their limits.)

Oddities
Not all ponies manifest their magic in the "proper" manner if their tribe. Some are sadly unable to do so, by injury or inborn defect - others demonstrate unusual powers, often linked to their talent. Some of these are common enough to be acknowledged as a "skill" - like beastspeaking - while others are more individual things, like the Stare. All draw on the same basic magic, though, and so follow measurable rules. And then there are the ponies which can do things that don't...