building computer?

Start with the newest motherboard you can afford. Make sure it will be forward compatible and that is it not branded to HP, DELL etc. NEVER buy anything from HP. They make disposable computers. According to HP a computer is out of date after 3 years and they do not offer updates (such as bios updates) that will support new hardware.

Once you have the mainboard, you can pick the other components to suit yourself. Maybe an I5 or i7 processor, some RAM, a hard drive and sound card and decent video card. You will be able to upgrade these to better ones later, but unless you have $15000 (a top end graphics card can run between $5000 and $7000 alone, but 2 years from now, you can probably get the same card for under $500.) to lay out all at once, buying slightly older versions (like last years models) will save you a lot of money, and still perform very well. Point is.. spend your money on a good motherboard first, then put together a PC you can game with now, and upgrade as you go, should you need to. You don't need to worry about getting 300 fps.. since you can only see 30 to 60 fps anyway.

No i3 should be perfectly fine for gaming, my friend has the same CPU and he's perfecly fine. Heaviest game he played is Black Ops III, I think and he's getting 60 fps on everything high (AA off). But yes get a GTX 1060 instead of that. He gets 60 fps in CPU intense games too, like Grand Theft Auto V. Your other parts are good, you should be fine. Have fun with that PC!

well the i3 isnt that good for gaming so if you could i would get an i5 cpu instead and i would get a gtx 1060 instead of a r9 280x.

Otherwise it is good.