Build your own AK. I see the price of AKs has risen dramatically since I last visited the United States, but a brand new AK is still cheaper than a badly used Garand, which is a lot cheaper than a G3.
The WWII Garand doesn't have a magazine, it has a clip, you put the clip into the rifle, and the clip is ejected along with 8th round. I don't know too much about the Garand, I've fired from one once, just one round. I can tell you this much - it is long and it is heavy. It's probably fairly accurate, but you only have 8 rounds before you have to load another clip. Eight rounds is not close to enough.
By modern standards, it's a very heavy gun. It's also very long. If you're thinking of getting either an AR or a Garand, get an AR. You could easily convert the AR into full-auto mode. You can easily stock up on dozens of 30 round clips for the AR. You can buy bigger magazines if you want, although they're far more prone to failure. The Garand was obsolete during WWII. AR and AK rifles are still competent. An AR is light enough that you could hold the pistol grip in one hand, extend your arm and fire it like a pistol. You can also fire it full auto this way, but, for me at least, it's uncontrollable for anything more than a short burst. Even though ARs feel like big air guns, they're pretty durable and dependable. I wouldn't even bother with a normal length AR, unless you really need the added accuracy. The longer the rifle, the harder it is to carry it around, especially if you're getting in and out of a vehicle or moving around confined spaces. For self-defense purposes, an AK or an AR will scare people more than a Garand.
As far as ammo is concerned, AK ammo (7.62x39) is probably the cheapest on the market. On the other hand, Garand ammo (.30-06 and .308) are at least twice more per round. It's a better round but isn't worth twice as much.
If you want power, I'd get an AK with a folding stock. If you decide you need more accuracy, I'd get an AR with a short barrel and a folding stock. If you want both, then go for an M1A with a shorter barrel and a folding stock (expensive). Personally, I would buy something extremely compact if I thought I'd have to carry it.
