I used to write everything from scratch myself. With that DX11 engine I tried to make, I basically didn't even use any libraries. I made my own math library, model importers, culling code, input handling, windowing, etc. It was all from scratch. I learned a whole lot, and I am grateful, but I wasted a lot of time. My versions were super basic, and I could have downloaded an open source library for free and had more features, less bugs, and saved months of effort. But it was a learning experience, so that is why I did it. If you actually want to finish anything, then download plug-ins, libraries, buy art or music, whatever you have to do.