Business buildings which cost diamonds are optional (i.e. premium) content. Not purchasing them won’t hinder your game progress. The game won’t require you to buy them unless you choose to do so. Buying them, however, will make your gameplay experience more enjoyable as these buildings not only look amazing, they are upgraded to level 5 and provide you with double XP when producing items. Also building the business provides you with a tourist boost and manager is available from the start