We recommend focusing on three important qualities: performance, compatibility, and price.
GPU performance is measured in-stream processors (SPs) which are executed per second. The amount of SPs determines the number of operations a GPU can perform each second. In addition, higher clock speeds and more memory bandwidth allow for faster rendering of images and videos by GPUs.
Finally, compatibility makes it possible for your motherboard to support your chosen graphics card. There are several standards to consider when deciding which one to use: PCI Express 3.0 vs. PCI Express 2.0 and HDMI 1.4 vs. HDMI 2.0 or DisplayPort 1.2 (we recommend that you go with DisplayPort 1.2). You need an appropriate motherboard in order to ensure that your PC be able to handle this hardware.
And lastly, don't forget to consider the price. GPU prices may vary greatly depending on performance, manufacturer, and release date but it's best to strike a balance between paying as little money as possible while still getting a powerful card.