You can use the GTX 1050 if that is available in your area, but the RX 460/GTX 1050 are similar in price/performance.
* The Mobo's for Kaby Lake are bit more on the lower end, so I would assume the price could drop down a few more $ in the coming weeks/months. You can use the H110 based Mobo's, but you would need to have the latest BIOS', in order to use Kaby Lake CPU's. Most of the H110 Mobo's here are about $40-60 and would fit into your budget a bit better.
* Of coarse if you need an OS, you won't be able to get a "Gaming" system, since the OS generally here in the U.S. would be 20% of your budget alone.
Another option would be refurbished PC with i5-2500K / i7-2600K, 8GB RAM, OS included for under $200, so you can spend the rest on GPU and PSU (if included PSU is not good enough).
Another option would be refurbished PC with i5-2500K / i7-2600K, 8GB RAM, OS included for under $200, so you can spend the rest on GPU and PSU (if included PSU is not good enough).
More than likely is to find an older i5 2400 or something like that, if they are available in the OP area. I have yet to see a used PC w/2500k/2600k, but I'm sure they are out there.