Clustering: How to cluster multiple CSV files that each represent a Steam user
You're likely going to have to do a little data wrangling to get the data in a better format. 

I'm assuming each file has a varying amount of rows, one for each game the user purchased? So, you could create one big matrix with the rows representing users and the columns representing games, and create an indicator matrix for to map purchases to games. Then potentially add additional columns per user including additional insight, like:


the number/percent of games purchased for each category(action, RPG, ...)
total purchases


Having data in that format may lend to more useful application of clustering algorithms.