David, Perceptive Apprentice

When David enters the battlefield, choose
an opponent to become your mentor.
Whenever your mentor casts a non-creature spell,
draw a card.
Whenever you cast a non-creature spell, your
mentor creates a treasure token.
{b}{u}, {t}: Until end of turn, you may cast target
card in an opponent's graveyard and spend mana
as though it were mana of any color to cast it as
though it had flashback.