I recommend learning a programming language first, since you can get the most power into your game, but If you don't want to learn a programming language go with Unity. It's by far the best software for someone who wants to make a FPS, but who does not have a full understanding of how to program a 3D game on their own. There are plenty of tutorials that can help you make 3D and 2D games. If you want to start off really basic, then maybe try GLBASIC, it's a BASIC programming language that allows you to make 3D games for Windows, Android, IPhone, etc. using a simple BASIC language.