If you only game, and only plan on gaming in the foreseeable future, the AMD FX line is an affordable choice that will provide great performance in games. If you want the CPU to last you for a few GPU upgrades, I'd recommend the FX-8350. If you don't plan on upgrading past a GTX 970 or equivalent, you'll be fine with an FX-6350 or an FX-8320. If you are looking for the bare minimum, the FX-6300 is still a great choice.
FX-8350: http://www.newegg.com/Product/Product.aspx?Item=N82E16819113284&cm_re=fx-_-19-113-284-_-Product
FX-8320: http://www.newegg.com/Product/Product.aspx?Item=N82E16819113285&cm_re=fx-_-19-113-285-_-Product
FX-6350: http://www.newegg.com/Product/Product.aspx?Item=N82E16819113327&cm_re=fx_6350-_-19-113-327-_-Product
FX-6300: http://www.newegg.com/Product/Product.aspx?Item=N82E16819113286&cm_re=fx-_-19-113-286-_-Product