Ideally, a person should put on a clean mask before going out, wear it until returning home, and then put the mask in the wash, wearing a clean mask for each trip away from the home. Since most people don't do their wash every day, enough to go between laundry days is ideal; a half-dozen or so. 

This is NOT, however, an ideal situation! When I considered the sheer number of masks required by my family, sewing them all seemed a daunting task. Start with one each and work your way up as you can. 

On the advice of my niece, who sent me the first  pattern (that I then modified,) I started with the smallest member of my family. That way, I could practice with the smallest amount of fabric. If I messed up, it would waste less fabric. After I figured out the process, I literally sewed the masks in order of who needed them the most. Once I got the hang of making them, it took me (and my elderly sewing machine) about an hour per mask, start to finish.