When to buy characters?

I'm finally getting into the game and just unlocked the third stage. I unlocked Poe and have been living in my garlic era since, but have some more characters I could buy. Is it worth it to spend the gold on them now if I don't plan on using them much anytime soon? I'm still trying to work on my power ups and have been prioritizing that. Is there anything aside from the characters themselves that you gain access to by obtaining more of them? Thank you