Spitebellows

Evoke doesn't change the timing of when you can cast the creature that has it. If you could cast that creature spell only when you could cast a sorcery, the same is true for cast it with evoke.

When you cast a spell by paying its evoke cost, its mana cost doesn't change. You just pay the evoke cost instead.

Effects that cause you to pay more or less to cast a spell will cause you to pay that much more or less while casting it for its evoke cost, too. That's because they affect the total cost of the spell, not its mana cost.