This is a tricky question as it depends on the man. For example, some men may want to start with a small bag that they can carry around their waist, while others may want to start with a larger bag that they can carry over their shoulders.
If you are peeking for a bag for your first purchase, it is best to start with something on the smaller side. This will let you get used to how the bag feels and its weight before investing in something more significant.