Thanks
, and my best wishes to you the coming days. I hope you manage to get Effie!
Speeding up the Witchy Cauldron is only 2 Gems, and it guarantees a Megan spawn. (so a guaranteed Prank Spellbook for 2 Gems + some energy to battle Megan)
It's cheaper than outright buying them via the Goal.
I would see how far you come the following 3 days, and then start speeding up the Cauldron for the Spellbooks you still need.
Keep collecting from the 3 Good Little Witches, every Megan spawn is a bonus + you also need the Elixer of Good.
I don't know if the Gem price in the Goal is for 1 book or for all the books you're missing. My Goals is gone/ completed so I can't see what mine says.
But I think speeding up the Cauldron is the cheapest way to go.