Well I'm gonna wait for the end of the event, go to the next age and then start collecting rewards from my new ageI’ve never bothered with the calendar and still managed to complete events. I suspect the calendar was intended for those that already had their playstyle to spend daily instead of in a single sitting
Thing is in order to complete the calendar you are very likely sacrificing at least 1 Upgrade through the Grand Prizes in order to get keys. That’s not a trade off I would be willing to make.
My advice? If you don’t believe you can complete the Calendar then ignore it, save your currency and spend the bulk in a single sitting later in the Event. For every day you spend without ending on a Shuffle you’re losing Grand Prize progress (shuffle gives free progress, presents reset progress each day)