The important part of your post, from my point of view, is your last sentence:
So do evocations create the energies from nothing (which goes against every known law of the universe) or does it work more like bending for avatar? either way i doesnt matter much just looking for input on how people think it works.
From my point of view, they're not creating energy from nothing and thus violating the laws of the universe; they're just accepting that the universe is rather more complicated than Physics normally allows for and bending those same laws.
To go back to your other thoughts, though... In my own head, it helps to think of it all as energy manipulation, with the proviso that it's strongly influenced by belief. It's all energy transfer. Setting something on fire? Creating fire - pouring pure energy into the region - or igniting fire - as you said, burning the oxygen in the air - and then directing it. Air? Applying energy to move the atmosphere around you. Water? Using energy to manipulate humidity, move water or whatever.
And sometimes the energy is more abusive of physics - actually converting one substance into another, like forming a cloud of poison gas in an otherwise normal room.
The most important thing to remind you of, though, and something that Harry brings up repeatedly, is that magic doesn't work if you don't believe in it. While it doesn't logically follow that magic *does* work if you *do* believe in it, it's blatantly clear that magic is shaped by the mind of the person causing it - and it colours it greatly. My hypothetical mage Hobbes's limits are completely different from my friend's hypothetical mage Calvin, simply because one was brought up on Dungeons and Dragons and elementalists and all that, while the other was brought up believing in psychics and ghosts and the Holy Templars channeling god's power. Neither is *wrong* - they just have completely different limits based on it.
So to actually give my answer to your question... What's earth magic? Is it ripping up concrete and earth, or is it creating "mystical rock" out of mid-air? Or something else? It just depends. The effect is the same (within reason), and so it's much more a matter of what you and your characters think... Because the "wrong" one won't work, by definition, since you don't believe in it. :-P