I use the "I want it formula". I look at a gun, check my wallet, if wallet exceeds gun price I buy it.

After I had a good shotgun, rimfire, 22 cal , 30 cal, and magnum cal, rimfire pistol, defensive pistol,hunting pistol,and mz loader,I realized i could no longer claim I needed a gun. I had to accept the fact I wanted it, and have learned to live with that.