http://uk.pcpartpicker.com/list/j3FXLD My spin on i3-6100 build. Get a (maybe used) case and voila. Upgrade path would be videocard, HDD for large file storage.
I would go with Pentium g3258-based PC in this budget and try using some second-hand components in it if possible/acceptable (
http://uk.pcpartpicker.com/list/hFtWZ8 ) Use just one of the ram suggestions added, obviously. 1150 socket is still plenty powerful and IIRC WOW loves high single-core productivity, which g3258 is great at, overclockable to 4.0 on stock cooler with hardly any effort.
As for the videocard, the idea is to save up some more on it + wait till rx480 is out, as it can cause prices to fall considerably. June, 29th is soon enough, stay strong.