Runaway Steam-Kin

Whenever you cast a red spell, if this creature has fewer than three +1/+1 counters on it, put a +1/+1 counter on this creature.
Remove three +1/+1 counters from this creature: Add {R}{R}{R}.

Young Pyromancer

Whenever you cast an instant or sorcery spell, create a 1/1 red Elemental creature token.

Infuriate

Target creature gets +3/+2 until end of turn.

Dragon Cultist

Commander creatures you own have "At the beginning of your end step, if a source you controlled dealt 5 or more damage this turn, create a 4/4 red Dragon creature token with flying."

Rile

Rile deals 1 damage to target creature you control. That creature gains trample until end of turn.
Draw a card.

Stun

Target creature can't block this turn.
Draw a card.

Warlord's Fury

Creatures you control gain first strike until end of turn.
Draw a card.

Expedite

Target creature gains haste until end of turn.
Draw a card.

Livaan, Cultist of Tiamat

Whenever you cast a noncreature spell, target creature gets +X/+0 until end of turn, where X is that spell's mana value.
Choose a Background (You can have a Background as a second commander.)

Shock

Thrill of Possibility

As an additional cost to cast this spell, discard a card.
Draw two cards.

Tavern Brawler

Commander creatures you own have "At the beginning of your upkeep, exile the top card of your library. This creature gets +X/+0 until end of turn, where X is that card's mana value. You may play that card this turn."

Seething Song

Faithless Looting

Draw two cards, then discard two cards.
Flashback {2}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Fists of Flame

Draw a card. Until end of turn, target creature gains trample and gets +1/+0 for each card you've drawn this turn. (A creature with trample can deal excess combat damage to the player or planeswalker it's attacking.)

Guttersnipe

Whenever you cast an instant or sorcery spell, this creature deals 2 damage to each opponent.

Kessig Flamebreather

Whenever you cast a noncreature spell, this creature deals 1 damage to each opponent.

Dragon Mantle

Enchant creature
When this Aura enters, draw a card.
Enchanted creature has "{R}: This creature gets +1/+0 until end of turn."

Captain Ripley Vance

Whenever you cast your third spell each turn, put a +1/+1 counter on Captain Ripley Vance, then it deals damage equal to its power to any target.

Electrostatic Field

Defender
Whenever you cast an instant or sorcery spell, this creature deals 1 damage to each opponent.

Mana Geyser

Add {R} for each tapped land your opponents control.

Crash Through

Creatures you control gain trample until end of turn. (Each of those creature can deal excess combat damage to the player or planeswalker it's attacking.)
Draw a card.