I was wondering if I could talk about my religion on my common app essay and how my religion has shaped me as a person. Is this a good route to go with?
Yep; it falls under the first prompt. Depending on what you write about with regard to religion, it might sound cliche so be mindful of that. Try to write about the unique experiences!
Religion can be a good topic to explore. Make sure that you are the agent of change in our essay and not your religion. It can be easy to fall into the trap of explaining your beliefs rather than exploring yourself and how your beliefs are a part of you. As with all essays, but in this case in particular, it is a good idea to have someone read over your essay. Good luck!