Walker of the Grove

Whether evoke's sacrifice ability triggers when the creature enters depends on whether the spell's controller chose to pay the evoke cost, not whether they actually paid it (if it was reduced or otherwise altered by another ability, for example).

If you're casting a spell "without paying its mana cost," you can't use its evoke ability.

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.