The correct answer is 1 more than you have.
I was taught from the time I was a kid that you only "need" 4 guns.
1. a big game hunting rifle.
2. a shot gun.
3. a pinking gun.
4. a self defense hand gun.
Shot placement is everything! I would rather take a round of 50BMG to the foot than a 22short to the base of the skull.
all 25 of my guns are 45/70 govt, 357 mag, 22 or 12 ga... I believe in keeping it simple