The cheapest graphics card you can play it on is an NVIDIA GeForce GTX 650. To play Flotsam you will need a minimum CPU equivalent to an Intel Core i5-650. Flotsam system requirements state that you will need at least 4 GB of RAM. You will need at least 1 GB of free disk space to install Flotsam.
Flotsam will run on PC system with Windows 7 and upwards.