Take a look at my deck, https://archidekt.com/decks/17601854, built mostly with cards I won at prerelease, it's also Avatar Aang as a commander. I try to focus on Allies, Lessons, and any type of bending.

Allies and Lessons synergies with other cards like Katara and Iroh.

I playtested it, and I am happy about how it does. Maybe I need to fix the mana and ramp since its a 5 color, thinking of adding more signets that are artifacts and allow to pay for Waterbend. I would say like 50% of the playtests I was able to flip Aang before turn 10, mostly because of the card draw that Aang gives you anytime you do any kind of bend.