Island

Scaled Nurturer

{T}: Add {G}. When you spend this mana to cast a Dragon creature spell, you gain 2 life.

Thrakkus the Butcher

Trample
Whenever Thrakkus attacks, double the power of each Dragon you control until end of turn.

Ganax, Astral Hunter

Flying
Whenever Ganax or another Dragon you control enters, create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")
Choose a Background (You can have a Background as a second commander.)

Song of Creation

You may play an additional land on each of your turns.
Whenever you cast a spell, draw two cards.
At the beginning of your end step, discard your hand.

Mountain

Lathliss, Dragon Queen

Flying
Whenever another nontoken Dragon you control enters, create a 5/5 red Dragon creature token with flying.
{1}{R}: Dragons you control get +1/+0 until end of turn.

Elemental Bond

Whenever a creature you control with power 3 or greater enters, draw a card.

Garruk's Uprising

When this enchantment enters, if you control a creature with power 4 or greater, draw a card.
Creatures you control have trample. (Each of those creatures can deal excess combat damage to the player or planeswalker it's attacking.)
Whenever a creature you control with power 4 or greater enters, draw a card.

Warstorm Surge

Whenever a creature you control enters, it deals damage equal to its power to any target.

Forest

Temur Ascendancy

Creatures you control have haste.
Whenever a creature you control with power 4 or greater enters, you may draw a card.

Miirym, Sentinel Wyrm

Flying, ward {2}
Whenever another nontoken Dragon you control enters, create a token that's a copy of it, except the token isn't legendary.

Ureni of the Unwritten

Flying, trample
Whenever Ureni enters or attacks, look at the top eight cards of your library. You may put a Dragon creature card from among them onto the battlefield. Put the rest on the bottom of your library in a random order.

Nature's Lore

Search your library for a Forest card, put that card onto the battlefield, then shuffle.

Dragon Tempest

Whenever a creature you control with flying enters, it gains haste until end of turn.
Whenever a Dragon you control enters, it deals X damage to any target, where X is the number of Dragons you control.

Sarkhan, Soul Aflame

Dragon spells you cast cost {1} less to cast.
Whenever a Dragon you control enters, you may have Sarkhan become a copy of it until end of turn, except its name is Sarkhan, Soul Aflame and it's legendary in addition to its other types.

Ketria Triome

({T}: Add {G}, {U}, or {R}.)
This land enters tapped.
Cycling {3} ({3}, Discard this card: Draw a card.)

Roaming Throne

Ward {2}
As this creature enters, choose a creature type.
This creature is the chosen type in addition to its other types.
If a triggered ability of another creature you control of the chosen type triggers, it triggers an additional time.

Quandrix, the Proof

Flying, trample
Cascade (When you cast this spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order.)
Instant and sorcery spells you cast from your hand have cascade.

Earthquake Dragon

This spell costs {X} less to cast, where X is the total mana value of Dragons you control.
Flying, trample
{2}{G}, Sacrifice a land: Return this card from your graveyard to your hand.

Rhythm of the Wild

Creature spells you control can't be countered.
Nontoken creatures you control have riot. (They enter with your choice of a +1/+1 counter or haste.)

Atarka, World Render

Flying, trample
Whenever a Dragon you control attacks, it gains double strike until end of turn.