Sparky, Biogenic Genius

+1: Add {u}{g}. Spend this only to cast creatures. If this mana is used to cast a creature, it enters the battlefield with a +1/+1 counter.
-3: Exile target creature. Its controller creates a 3/3 green dinosaur dragon token.
-7: Choose a creature from any graveyard. Create a token that's a copy of that creature except it also has Hexproof, Menace, and Haste.