Best bang for buck would be to build the PC yourself.
Going down the route of which processor is going to be the big decision the new AMD Ryzon's are getting very good reviews, however still not getting the same gaming performance as Intel chips.
But keep in mind on most forums nowadays most are recommending the new AMD chips, this is due to having more cores and games have not been optimised to use the chips yet.
The 1700x seems to be the chip to go for..
Or if you choose Intel you can get either the i7 7700k or i5 7600k, both perform very similar, but you get bragging rights of owning an i7.
Personally if your building a gaming PC I would get an Intel.
Motherboard wise I only buy ASUS, as had trouble with other boards in the past.
There are plenty of options available:-
Cheapest I would get:-
ASUS Z270-PRIME
Next best:-
ASUS Z270-STRIX E or F
Decent for gaming:-
ASUS Maximus-IV Hero
GPU nothing better than a 1080ti.