I would get a .22 rifle with a scope, this would be for practice and target shooting.
A 12 gauge shotgun like an 870, or maybe a reliable autoloader if you need one for target shooting. I'd keep this because it would double as my self-defense gun and hunting gun, if I was limited to 3 guns. (I live in a slug-only area) A 9mm like a g19, or .357 revolver. 9mm ammo is very cheap, .38 ammo is cheap but not as much as 9mm, and 9mm and .38s or .357s could still be used for self-defense. (No dangerous critters where I live.)