I have been learning GPUs and how to best use them. And its not easy. You can't use GPUs to just make your CPU things faster, CPU and GPU are good at different things. Many algorithms are very annoying and slower on the GPU so it makes sense to do those on the CPU, while very parallelizable tasks can be quite good for the GPU. Most algorithms end up being a hybrid where CPU sets up the data in a way that makes it easy and fast for GPU to do its thing.
I have written a nim-to-glsl compiler that might start you off: <https://github.com/treeform/shady> . It does both vertex and fragment shades you might use for games and compute shaders you might use for more "general" computing.
