Secondary stats make the majority of your gearing decisions but they are usually kind of confusing and for most people it isn't very clear how do guide writers come up with the specific recommendations they give besides "it's what the sim says". While it is true that this is a tool best left for the robots because it can get complicated really quickly there are still some basic rules that you can know to give you a better idea of how you should be picking stats and maybe even let you make decisions that are good for you but can be different from what someone else recommends.