I have to say the Ryzen 7 1800x is a better processor for a gaming enthusiast versus any of these Thread Ripper processors. The Thread Ripper is mainly for Content creators and heavy multitasking usage with all the available threads and cores it will be able to tap into and utilize, versus any of the other (AMD Processors) by a long shot. The Ryzen 1800x would be better as it can use the base frequency of 3.7Ghz - 4.1Ghz per core at 2 theads per core, it has a total of 8 cores and 16 threads and will also supports 4K & VR.
Now this processor supports 2667 Mhz front side bus at Max, so I would purchase 2 (Dual Channel memory each at 8GB DDR4 clocked at 2667 Mhz RAM which is the max frequency that this processor will handle, anything higher is a waste of money because it will not utilize a higher frequency and I would also make sure that it is a low latency memory.
Now moving on to the motherboard make sure it obviously supports the ryzen processor socket series & make sure that it also supports 2667 Mhz FSB, having a good chipset like x370 is important and support wireless N/AC, gigabyte ethernet, has a 6GB/s SATA connection, supports Dual Channel Memory slots, USB 3.1, HDMI 1.4 ,16x pcie any other features is up to you. a Ceative Sound Blast Z sound card would top it off nicely.
Choose your power supply needs accurately those are the essentials.
Overall make sure to pick the best graphic cards suited for the max resolution of your gaming monitor, because the graphic card is what will really drives your system, but you dont need to go overboard beyond that.