Experiment One

Evolve (Whenever a creature you control enters, if that creature has greater power or toughness than this creature, put a +1/+1 counter on this creature.)
Remove two +1/+1 counters from Experiment One: Regenerate Experiment One. (The next time this creature would be destroyed this turn, instead tap it, remove it from combat, and heal all damage on it.)

Mountain

Rubblebelt Maaka

Bloodrush — {R}, Discard Rubblebelt Maaka: Target attacking creature gets +3/+3 until end of turn.

Gather Courage

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
Target creature gets +2/+2 until end of turn.

Fresh-Faced Recruit

During your turn, Fresh-Faced Recruit has first strike.

Rampaging Rendhorn

Riot (This creature enters with your choice of a +1/+1 counter or haste.)

Burning-Tree Vandal

Riot (This creature enters with your choice of a +1/+1 counter or haste.)
Whenever Burning-Tree Vandal attacks, you may discard a card. If you do, draw a card.

Gruul Guildgate

This land enters tapped.
{T}: Add {R} or {G}.

Drudge Beetle

Scavenge {5}{G} ({5}{G}, Exile this card from your graveyard: Put a number of +1/+1 counters equal to this card's power on target creature. Scavenge only as a sorcery.)

Gruul Guildmage

({R/G} can be paid with either {R} or {G}.)
{3}{R}, Sacrifice a land: Gruul Guildmage deals 2 damage to target player or planeswalker.
{3}{G}: Target creature gets +2/+2 until end of turn.