What is the best subnet mask for a network?

As a seasoned practitioner in the realm of cryptocurrency and finance, I'm often faced with intricate technical questions that require a nuanced understanding of networks and their components. One such query that frequently arises is: "What is the best subnet mask for a network?" This question begs for a thorough examination of the network's specific requirements, such as the number of devices it needs to support, the desired level of security, and the overall topology. The answer isn't a one-size-fits-all approach; it's tailored to each network's unique circumstances. With this in mind, how do you approach determining the optimal subnet mask for a given network?