Depends on how many firearms you have already. I would say more guns until you at least of two copies of a good battle rifle or carbine (e.g., M1, M1A, FAL, AK or AR15) and a handgun such as a Glock, 1911, XD, M&P, SIG, HK, etc. One primary rifle and handgun are not enough. Things break at the worst times so always have a second in ready reserve exactly like your primary. You might want at least one defensive shotgun.
Then make sure you have twice the mags as you foresee wanting to be ready for each gun (at least 10 each).
After that you should have at least 1000 rounds for each primary weapon, and either additional reloading components or additional ammo. Focus ammo stockpiling on your primary rifle and handgun cartridges, don;t be thin across twenty different cartridges.
Then I would stock up on a couple of sets of repair parts for each primary weapon: firing pin, extractor, ejector, springs, pins, bolt or bolt carrier group if AR15, etc. Some weapons are especially easy to stock up on complete repair parts: Glock, 1911, Hi-Power, M1, M1A, FAL, AK, AR15.
After all this then you could work on a third set for a second person in your household, and so on.
Many of us get into variety and end up with not enough redundancy for extended defensive purpose when repairs and parts may not be readily available.