Installing Tensorflow with GPU requires you to have NVIDIA GPU. AMD video cards are not supported with tensorflow. NVIDIA uses low level GPU computing system called CUDA. It is an NVIDIA proprietary software.
One can go the OpenCL way with AMD but as of now it won’t work with tensorflow.
Also, all NVIDIA devices are not supported. Here is a list from the NVIDIA documentation listing the supported GPUs.
By the end of it, Vivek also shows us a simple trained model.