Plains

Sol Ring

Boros Signet

Arcane Signet

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

Kaldra Compleat

Living weapon
Indestructible
Equipped creature gets +5/+5 and has first strike, trample, indestructible, haste, and "Whenever this creature deals combat damage to a creature, exile that creature."
Equip {7}

Clifftop Retreat

Clifftop Retreat enters tapped unless you control a Mountain or a Plains.
{T}: Add {R} or {W}.

Sacred Foundry

({T}: Add {R} or {W}.)
As Sacred Foundry enters, you may pay 2 life. If you don't, it enters tapped.

Don't Have

Nahiri, Forged in Fury

Affinity for Equipment (This spell costs {1} less to cast for each Equipment you control.)
Whenever an equipped creature you control attacks, exile the top card of your library. You may play that card this turn. You may cast Equipment spells this way without paying their mana costs.

Command Tower

Mountain

Arid Mesa

{T}, Pay 1 life, Sacrifice Arid Mesa: Search your library for a Mountain or Plains card, put it onto the battlefield, then shuffle.