Pub is the best way to get cheap gold keys. Almost half the cost of grocery.
Gold keys give world fruits on event so it is beneficial to optimize the amount of gold keys you can get from Pub! Always roll till you get any 7 or 6 star task, or if you get any 5 star or 4 star tasks that have diamonds or gold keys.
ALWAYS SAVE TWO 7 STAR AND FIVE 6 STAR TASKS FOR EVENT AND PUBS IN GENERAL FOR TYCOON EVENT.