Go for a amd r7 265 . Budget friendly gpu. Bottlenecking is where you do not get full performance from a gpu or what ever- e.g. A intel pentium at 3.4ghz with a titan Z. U will be bottlenecking like a motherfucker.
That would go well with a R9 270 from AMD or GTX660 from Nvidia. If you have 64bit OS then the ram would be better as 2 x 4GB, 4GB would be the bottleneck.