I am in love with philosophy. The practice of philosophy helped liberate me from religion, opened my eyes to new ideas, and made me into a better person. However, I am studying philosophy now in college and am increasingly losing "passion" in the study because I am unable to fully grasp the ideas/concepts of philosophers such as Leibniz, Spinoza, Descartes, etc. I don't know if you formally studied philosophy, but do you think it's essential to know the concepts and ideas of these people?

I’m going to refer you to one of my good friends and philosophers, Philosopher’s Dog.  She is also an atheist and focuses much more on the philosophical aspects of both religion and of life.  She’s brilliant.  She should be able to provide you with some guidance.