xxlynchninja11xx

600$ is a tight budget so building a rig is probably the only way to go. Get an used I5-3570k or 4460 with a R9 270X. If you are willing to build, I can teach you and put together parts and walk you through the process. It's not that hard and actually quite simple. Feel free to PM me :)

I have to agree with what he said. An AMD build can run low $800 to mid $1000 and is really good. I run an AMD6300Fx at 5.0Ghz with a 8gb ram an GTx780 for about $950 is when I built it. Just look and shop around for parts

AMD is cheaper then intel, Intel is expensive because its a fully unlocked processor meaning more stability in games, I have an 8350 and the Sapphire R9 290X and i run GTA V and Arma 3 at more then 60 fps, and everything is stock even the processor speed at 4Ghz. Build your computer, because then you have more control over what goes in it as i build computers for a living. But if you dont know how, then buy one fully built. although you can build your own with the tons of computer building videos out there, theres even people that show you how to build  budget systems, look on youtube. You really dont want a laptop really for gaming as laptops unless you get a gaming one are not designed for Gaming and you will have lag issues. Do some research and if you want a good computer hit me up with a price range in a private chat and ill throw you one thats built already.

one: for arma 3 you want an intel processor
two: any GPU with 100+ clock speed and 2 Gigs of VRAM
 
you should be good then but arma 3 and AMD dont mix, only get 20 FPS with a gtx 960 and an AMD 8320 on arma 3, i can max out gta 5 with 60 fps