Foundry Street Denizen

Whenever another red creature you control enters, Foundry Street Denizen gets +1/+0 until end of turn.

Legion Loyalist

Haste
Battalion — Whenever Legion Loyalist and at least two other creatures attack, creatures you control gain first strike and trample until end of turn and can't be blocked by creature tokens this turn.

Hobgoblin Bandit Lord

Other Goblins you control get +1/+1.
{R}, {T}: Hobgoblin Bandit Lord deals damage equal to the number of Goblins that entered the battlefield under your control this turn to any target.

Den of the Bugbear

If you control two or more other lands, Den of the Bugbear enters tapped.
{T}: Add {R}.
{3}{R}: Until end of turn, Den of the Bugbear becomes a 3/2 red Goblin creature with "Whenever this creature attacks, create a 1/1 red Goblin creature token that's tapped and attacking." It's still a land.

Goblin Arsonist

When Goblin Arsonist dies, you may have it deal 1 damage to any target.

Conspicuous Snoop

Play with the top card of your library revealed.
You may cast Goblin spells from the top of your library.
As long as the top card of your library is a Goblin card, Conspicuous Snoop has all activated abilities of that card.

Lightning Strike

Lightning Strike deals 3 damage to any target.

Rundvelt Hordemaster

Other Goblins you control get +1/+1.
Whenever Rundvelt Hordemaster or another Goblin you control dies, exile the top card of your library. If it's a Goblin creature card, you may cast that card until the end of your next turn.

Mountain

Squee, Dubious Monarch

Haste
Whenever Squee, Dubious Monarch attacks, create a 1/1 red Goblin creature token that's tapped and attacking.
You may cast Squee, Dubious Monarch from your graveyard by paying {3}{R} and exiling four other cards from your graveyard rather than paying its mana cost.