The firearms in your battery will depend on what that battery is used for.
A supply for an infantry platoon for 90 days will be different from a Boy Scout Troop's 90 day supply.
Will you be training newbies? If so, try to get Airsoft or pellet guns that are almost identical to what you shoot.
Now, for the firearms.
For plinking, nothing beats a .22LR. It can be single shot, pump, lever, or semi-auto. .22LR ammo is MUCH cheaper than anything else. The Ruger 10/22 is one of the best .22LR rifles ever made, and its' price reflects it. .22LR is about the only rim-fire caliber I shoot. The rest are center-fire.
For hunting anything bigger than a rabbit that does not fly, the preferred choice is a center fire, scoped, bolt-action rifle in .308 or a similar caliber. Other options include .30-06, .243, etc.
For self defense (against humans, snakes, etc.) a handgun is ideal. The bad guys only need a gun for 5 minutes to rob someone, but a good guy need his/her gun 24/7 for years before something bad happens. Therefore, always be armed. There are 2 common kinds of handguns: semi-autos and revolvers. Please note that revolvers and semi-autos almost always use different ammunition. I like semi-autos for their flatter profile and their higher capacity. The names here are many: Glock, Beretta, CZ, Ruger, etc. Pick one you like, and that you can comfortably carry. There is a lot of talk about "stopping power" (except here at CPF.) Larger diameter bullets stop bad guys better, to stop the bad guy from harming your family. A .32 will be MUCH weaker than a 9mm (which is usually considered a minimum for self defense.) A 9mm will be much weaker than a .40 or .45. Having said that, correctly placing your shots will be FAR more important that using a large bullet. If you plan to carry a handgun, I suggest that you (1) learn the laws, (2) learn to carry it, and (3) compete in
http://www.IDPA.com or a similar practical shooting sport.
A rifle is always better than a handgun. For serious self defense, serious fun in IDPA-style sports, or serious hunting (e.g., hogs) a semi-auto rifle is needed. Semi-auto rifles allow more rapid and (in the right hands) more accurate fire. Military style rifles are the best, as they are nearly indestructible. M1 Garands, M14s, FALs, H&K G3s, AK47s, and M16s are common. These weapons have a larger ammo capacity, are simpler, more rugged, and are often available surplus. It's a common misconception as to which is more powerful: an AK or a deer rifle. The AK is far weaker than the deer rifle, as the deer rifle has to stop a large, wild animal humanely. A military rifle only has to would a relatively weak and thin-skinned human. If man eating aliens invade, you will need an AK47.
For bird hunting, a shotgun is ideal. I don't hunt birds.
Other shotguns are great for hunting small woodland & upland creatures. I don't hunt those little guys.
Still other shotguns are used for self defense. They are the most devastating weapons this side of C4. They have a limited magazine capacity, but if you need more than 6 rounds of 12 gauge you also need air support. 6 quick blasts from a pump shotgun will put more lead in the air more quickly than a full-auto UZI. An experienced shooter can switch between slugs for near-rifle-accuracy, buckshot for taking on large targets, and bird shot that will not penetrate walls. This versatility is unmatched.
Some specialty guns include pocket pistols (very small, .22 or .32 pistols,) varmint rifles (that shoot very small bullets very fast for picking off small woodland creatures at a fraction of a mile,) reproductions of military arms that do shoot, but really exist to look cool (e.g., MP44s and PPSH 43s.)
If I had a .22 rifle, a pistol, a deer rifle, and a shotgun, I would feel well armed.
Along with the firearms, get cleaning supplies, ammo, magazines, holsters, slings, manuals, reloading tools, and spare parts. The amounts of these depend on what you plan to use the guns for. During peace time, a gun is much more expensive than 1,000 rounds of ammo. During the "civil" war in the former Yugoslavia, an almost factory, NATO marked new Beretta 92F with 5 mags was traded for 3 mags of 9mm ammo. (During wars, ammo gets shot up, but guns last longer than the soldiers carrying them.) If aliens invade tomorrow, you would be better off with 2 guns and 5,000 rounds of ammo than with 5 guns and 100 rounds of ammo.
Andy