All of my resources? Of course not. Some of my resources? Sure. You can buy a good defensive pistol for about $600, and spend maybe $1000/year on training and practice, including ammunition, and be well-prepared. I spend and do more because I enjoy competition shooting, but that's a case where my hobby helps me be prepared rather than being preparedness spending.

You don't need a gun until you need it badly. With that said, if your resources are constrained such that you can carry a cellphone or a gun but not both, carry a cellphone.