Well first you need to look at the ammo types and what is most numerous, reliable, and has stopping power. First for home defense you need two
pistols, and if you can afford I would go with the P.226 as it is realiable, has great stopping power, easy to carry/reload and is deadly accurate for
its class. If not, a Sig 9mm of HK 9mm (your choice of model) would be a good choice. For your wife, 9mm is probably as high as you want to go caliber
wise for her to control effectively. Also find one for her that recoils down, helps beginners short more accurately (most HKs do this). For mid range
the M4 carbine is good, most ARs also, but remember they are light gus that can jam when dirty easily. AKs are essentially clubs that can fire .223
rounds fast, generally no matter what condition they are in (not SKS chinese models or romanians, they suck). Given your abilities with the rifle, I
say bushmaster AR 5.56 is your best bet. Remember, .223, .224, 9mm and .22 rounds will probably be the most plentiful around, followed by 7.62, 5.56
and .45 rounds. Rare ones would be magnum rounds, 10mm, .308 rounds and .32s.
One thing I HIGHLY recommend is a .22 caliber semi-auto rifle. Might be a pea shooter, but its quiet, accurate at short ranges and can be used to hunt
small game for food, and easily can kill another person if need be. Also, you can store thousands of rounds for .22s in almost no space, I have 20,000
rounds of it at our home in florida, we will never run out.
You also need a couple good shotties (probably best weapon for your wife to use, mine would use a shottie) for defense. Mossbergs are great cheap 12 g
that are fairly durable, but if you can spring for 980 or a benelli even I would. 12 g buckshot for defense ammo, 12 g bird shot for hunting, 12 g
slugs if you feel you need them (these really are not needed). Last get a good long range rifle with a scope, I've got a a Remington 30.06 hunter
with 300 yrd scope and pump action 6 round internal clip. Its heavy, mean, loud and damn accurate (put a hole in a V8 engine block). Stay away from
.50 cal weapons, you simply cannot use them effectively if you are not trained.
Lastly stock up on clips, belts, ammo cases, spare parts if you can like bolts, firing pins, springs, etc...
oh and buy wholesale gun cleaning supplies. Remember, a clean gun is a happy gun.