Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Goblin King

Other Goblins get +1/+1 and have mountainwalk.

Goblins of the Flarg

Mountainwalk (This creature can't be blocked as long as defending player controls a Mountain.)
When you control a Dwarf, sacrifice Goblins of the Flarg.

Cave Sense

Enchant creature
Enchanted creature gets +1/+1 and has mountainwalk. (It can't be blocked as long as defending player controls a Mountain.)

Sol Ring

Blood Moon

Goblin Lackey

Whenever Goblin Lackey deals damage to a player, you may put a Goblin permanent card from your hand onto the battlefield.

Burrowing

Enchant creature
Enchanted creature has mountainwalk. (It can't be blocked as long as defending player controls a Mountain.)

Goblin Spelunkers

Mountainwalk (This creature can't be blocked as long as defending player controls a Mountain.)

Goblin Mountaineer

Jeweled Lotus

{T}, Sacrifice Jeweled Lotus: Add three mana of any one color. Spend this mana only to cast your commander.