I recommend an any variant of the AK-47, they are relatively cheap and extremely durable (avoid the Egyptian ones, they’re absolute crap). They’ll fire even if they’re full of gunk and grit, whereas the M-16 family starts malfuntioning the second it even starts to get a little bit dirty (sorry guys, but it’s true). Get at least a thousand rounds of ammo. Seems like a lot, but it goes quickly. As for pistols, I’d get a full-size 9mm, the Taurus knock-off of the Beretta is very affordable. (If you’re a M-16 lover, please don’t flame me for telling the truth, I’ll only spread it more if you do. Nice on the range, LOUSY for combat conditions)
For 99.9% of us, the AR-15 will work fine. I’m too old for crawling around in the dirt and worrying about jam ups. Besides, I have an M1 Garand that will work just fine.