If you are free-kick like I am, unless you really want a certain character or two - make sure to save up your donuts.
Sometimes during events, we can get offered rebate deals like the ones that happened most recently for Chester and Professor Frink during the most recent sci event.
Also a big rebate sale for premium characters is almost definitely gonna happen during next month's Black Friday sales. So I would personally recommend to hold off buying any premiums until then.