I have saved 100 gems and thinking of keep saving for a wizard but not sure if I would use it as I don't play on Facebook (my game isn't even connected to it yet).
Some sites say they speed up anything, wiki says they just speed up food and hatching.
Do they speed up the temporary tournament wait times? I can see this being very useful as some wait times cost more than the wizard costs.
Do they give much of an advantage in the heroic races?