Spices are surprisingly expensive. As I've started cooking I've quickly realized that it becomes a lot less expensive to make a dish once you accumulate a few basic spices.
I've found myself finding a recipe online at work, printing it off to make for dinner and picking up the necessary ingredients on my way home. But every time I tried that I could never remember whether or not I already had the needed spices.
So I decided to make a list of every spice that I currently have and keep it in the note section on my iPhone. This way I always know what I need to buy without duplicating any of the spices I already have.
I also looked up a few suggestions of the 10 spices everyone should keep in their pantry (other than your basic salt and pepper). These were the most common 10 I found.