Here's what I would do:
Pay attention during the games you play. You will notice that you are getting killed by certain strategies used by specific champions. The damage summary when you die is useful. Eventually, you will come to dread meeting certain champions during the starting splash screen.
Those are the champions you want to learn how to play. Why? Because after you play them, you'll begin to see their weaknesses as well as their strengths. You will learn how to counter them, and in the meantime, you will naturally learn which champions you have the most fun with. After all, would you ask someone else what your favorite color should be?