The cheapest graphics card you can play it on is an NVIDIA GeForce GTX 970. CubeWorks system requirements state that you will need at least 4 GB of RAM. You will need at least 4 GB of free disk space to install CubeWorks. To play CubeWorks you will need a minimum CPU equivalent to an Intel Core i5-4590.
CubeWorks will run on PC system with Windows 7 SP1 or newer and upwards.