custom Avatar RPG (only if you've watched the show.)

[Mystic Muse]

I'm making an avatar game for my cousin since it's one of his favorite shows. the way it works is the game ends at level twelve or whenever I can finish up the campaign. I have one question. every player gets all their best abilities at level ten. with this in mind at which point should each character with the element required get
lightning,metal bending, lava bending, sand bending and blood bending?

the game is based off D&D 3.5 with a smaller level cap.

please inform me if this goes against forum rules. I don't think it does but it might.

[Radiun]

Perhaps those bending styles could be feat chains.
Not all Earthbenders feel the world with tremorsense like Toph, but it seemed like a prerequisite to feeling the impurities in metals for metal-bending, and it can be learnt as Aang did

[Kuma Kode]

Not sure, but you could possibly check out Avatar d20 for inspiration.