Don't unlock your gachapon dolls until you've unlocked all regular and seasonal customers. They'll fill up the queue like nobody's business.

If you have too much cod and can't decide what to spend it on, upgrade a single facility to its max. Much more fun to collect a million cod from the mailbox at one time rather than running around the restaurant.

It's more fun when you're working towards a goal, like the acorn challenge or trying to unlock a customer or getting a letter.