Vraska's ultimate ability will sell this card! It's a fun win condition and it's not that hard to get in token-based decks. You can sacrifice them using the +2 ability, which will draw you additional cards, and in just three turns you can activate the -9 ability.
Her color pie hints on synergy with Saprolings, and probably in Standard that's where things are headed. As for Modern and Legacy, Vraska will most likely see play in graveyard-based decks.
Currently, she is priced rather modestly for a planeswalker, but if it proves to be as good as her ultimate ability tells us, then that price tag will go up in no time.