Declare Treasury Thrull and the mana-producing creatures as attackers.
Treasury Thrull triggers, returning Dryad Arbor to your hand from your graveyard.
Move to your postcombat main phase.
Cast Waves of Aggression from your graveyard for its retrace cost by paying ({3} magic symbol) ({RW} magic symbol) ({RW} magic symbol) and discarding Dryad Arbor, untapping all creatures that attacked this turn, and causing you to get an additional combat and main phase after this one.
Activate the mana-producing creatures by tapping them, adding at least ({3} magic symbol) ({RW} magic symbol) ({RW} magic symbol) .
Move to your next combat phase, and declare Treasury Thrull as an attacker.