Classifying customer frequency

Given the following dataset, classify customer value based on order frequency. You can assign them a score of 1-3, with 1 being least valuable and 3 being most valuable For example, a customer who has made 10 purchases is more valuable than one that has made 2 purchases across the same time period.

For more information regarding customer lifetime value you can read this post.

Note that this question is a part of a series of questions that will build off of each other.