I'm not sure how the pricing of components compares where you are, but if gaming performance is your primary concern, it might be worth spending less on the CPU and motherboard, and putting that toward a somewhat higher-end graphics card. In most games, one of the 8th or 9th gen 6-core i5s should offer gaming performance that's pretty close to what the i7s have to offer. See the performance summary in this recent review, for example (scroll down past the CPU tests to the gaming tests)...
https://www.techpowerup.com/reviews/Intel/Core_i5_9600K/19.html
Also, note that those tests were performed with the CPU paired with a very high-end 1080 Ti graphics card. With a GTX 1060-level card, the graphics hardware would be limiting performance in most games more than anything, and at 1080p. the average performance difference would be more like what you see in the 2160p (4K) chart there. In other words, the CPU shouldn't matter that much, since the graphics card will be what's usually limiting performance.
Now, compare the performance differences in this recent graphics card review...
https://www.techpowerup.com/reviews/NVIDIA/GeForce_RTX_2060_Founders_Edition/33.html
As you can see, the graphics card will typically make a much larger difference to gaming performance than the CPU, so it's probably worth spending more money on that than on the CPU and motherboard. Even something like an i5-8400 on a B360 motherboard with a GTX 1070 should generally perform better than an i7-8700K on a Z370 board with only a GTX 1060, at least as far as gaming is concerned.