It's Relative
Before we start, keep this in mind: 5 sprays of perfume X can be equal to 15 sprays of perfume Y, so everything I write in this entry is based on an “average” perfume. How many sprays you should use is completely relative, because some people want everyone around them to smell their fragrance, while for others this is not that important. If it is not very important to you that everyone notices your scent, then around 5–6 sprays in total on both your skin and clothes will probably be enough for what you want. But if you want your perfume to be noticed, you should spray more of it on your skin. Roughly speaking, on a day when you use 10 sprays on your skin and 4 sprays on your clothes, your perfume will probably be noticeable. Again, these are only “average” numbers. What perfume you are wearing is much more important than the number of sprays.
Consider the Environment
You should also consider the environment when applying your perfume. For example, if you are going to spend most of the day outside, you can spray a little more, but if you are going to be in an office, using less will be better both for you and the people around you. Again, the perfume you choose is very important here. Even 3–4 sprays of a very strong perfume can still be enough to overwhelm everyone in an indoor space, so you should also adjust your fragrances depending on the environment and the season.