Firebending Lesson

Kicker {4} (You may pay an additional {4} as you cast this spell.)
Firebending Lesson deals 2 damage to target creature. If this spell was kicked, it deals 5 damage to that creature instead.

Iroh, Grand Lotus

Firebending 2
During your turn, each non-Lesson instant and sorcery card in your graveyard has flashback. The flashback cost is equal to that card's mana cost. (You may cast a card from your graveyard for its flashback cost. Then exile it.)
During your turn, each Lesson card in your graveyard has flashback {1}.

It'll Quench Ya!

Counter target spell unless its controller pays {2}.

Combustion Technique

Combustion Technique deals damage equal to 2 plus the number of Lesson cards in your graveyard to target creature. If that creature would die this turn, exile it instead.

Hermitic Herbalist

{T}: Add one mana of any color.
{T}: Add two mana in any combination of colors. Spend this mana only to cast Lesson spells.

Fire Nation Cadets

This creature has firebending 2 as long as there's a Lesson card in your graveyard. (Whenever this creature attacks, add {R}{R}. This mana lasts until end of combat.)
{2}: This creature gets +1/+0 until end of turn.

Mountain

Accumulate Wisdom

Look at the top three cards of your library. Put one of those cards into your hand and the rest on the bottom of your library in any order. Put each of those cards into your hand instead if there are three or more Lesson cards in your graveyard.

Uncle Iroh

Firebending 1 (Whenever this creature attacks, add {R}. This mana lasts until end of combat.)
Lesson spells you cast cost {1} less to cast.

Shared Roots

Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Forest

Sokka, Lateral Strategist

Vigilance
Whenever Sokka and at least one other creature attack, draw a card.

Boomerang Basics

Return target nonland permanent to its owner's hand. If you controlled that permanent, draw a card.

Sokka's Haiku

Counter target spell.
Draw a card, then mill three cards.
Untap target land.

Island

White Lotus Hideout

{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to cast a Lesson or Shrine spell.
{1}, {T}: Add one mana of any color.

Bender's Waterskin

Untap this artifact during each other player's untap step.
{T}: Add one mana of any color.