Building a new Computer

Looks good for a mid-range gaming rig.

Okay... I'd need to know prices on the stuff you're listing there in order to be specific... But...
General answers:

HD7850's are rather hard to find anymore and usually overpriced as hell by 3rd party retailers atm. You're likely going to be better off buying an R7 260x 2GB card instead, or maybe even an R9 270.

That RAM is pretty terrible for DDR3 1600 (Very high latency, 11-11-11-30). Unless you're just getting a superb deal on it, I wouldn't touch it.

That's a TERRIBLE motherboard. It's a 700 series chipset so it will not support USB 3.0 or SATA III (6GB/s). Again, unless you're getting just an outright amazing deal and cannot afford something better, that's a horrible investment as you're buying something already 3 years+ out of date.

There's basically ZERO reason to buy a SATA III SSD, when you're buying a MoBo that won't support it. You won't even see the speed of that drive, making it a terrible investment. If you're budget is that tight, leave out this pointless SSD, and put that money into buying a halfway decent motherboard instead.

Case, eh, whatever. I like the HAF series well enough, and have a 932 myself. I love the airflow.

Corsair CX series PSU... I wouldn't buy this either. Corsair PSUs are very hit or miss, and their only good ones are those that are rebranded SeaSonic PSUs. It's likely cheaper and better to just buy a SeaSonic directly.

And the CPU: The FX series 6 core CPUs are actually somewhat lackluster compared to the Thuban 6 cores, but should be decent. You'll probably be better off just going with a faster Quad core though, unless you do a hell of a lot of multi-threaded tasks.

So... Really, I've seen worse, but I would not build this myself, and would do all I could to keep a friend from doing so, unless they were getting just an absolutely incredible deal: ie: they were getting that full kit for under $500 US.

Edit: Just noticed the USB3 line there and checked, Gigabyte added USB3 support on that particular MoBo, so that part is moot. It does, however, still not support SATA III. I also checked the MoBo out on the manufacturer page, and they have a warning informing that it will not support FX CPUs by default, so if you buy that MoBo you're going to also have to download a BIOS update and be able to do your own flashing of the BIOS for it to enable FX CPU support.

well i also need computer parts ...i have limited budget 200$

You can't go wrong with adding a water cooler. Especially if you want to over clock one day. I recommend the CORSAIR Hydro Series H60. Have you considered using a modular power supply? It does make quiet a difference with cable management. Perhaps a SeaSonic M12II 620 Bronze 620W? As for the RAM, look into something with a lower latency. I like G.SKILL Ripjaws X Series 8GB DDR3 1600. I love their customer service too.