I know what you mean....I worked up the directions for a pattern in a magazine for a retreat. the amount given was about like what you have there.
So. Look first and see if all the prints are about the same value. If so then it is easier. Then look to see how each block is constructed. Are there very darks or lights in it. Fortunately my case had all about the same value.
Then choose 5-8 prints in each color group. It just depends on how the colors are used in the pattern.
Can you give the source for the pattern or post a picture that will give some idea of what the finished product will look like.
I decided in my case that the "designer" had access to all the fabrics in a certain line from one fabric company. Yours may be the same and the total mix is what they worked with.