In studio and on location photo shoots can be more productive with planning. Consider adding an alternative shot to contrast what you are doing to add more content to your looks. Think about simple changes in the style, lighting or angle that will add value to the shoot.
You will read all sorts of numbers thrown out there that should be in your portfolio or book. Some of the numbers are stating 20 and 30+ images. I would agree that if you were an established international star of modelling then this is probably the number you should have. However this is not where anyone starts.
Start with the fundamental 7 and constantly build and edit.