I helped my friend run Terasology from source via Discord. He had almost nothing installed other than a Java IDE, so we had to start from the very beginning. First we installed Git Bash to make it easier to interact with GitHub for parts of the task where it was required. This was the hardest part of the entire process because of all of the options in the installer, but even then it was relatively easy. He also didn't have a GitHub account, but that didn't take long to create. After that, getting the game up and running was a breeze. The instructions are so simple I was able to give them to him from memory and getting it to properly run from source didn't take long at all.
Next, we added a simple block, which went quickly as well. Forking and cloning the Sample repository went well, and adding the block itself was very simple. Getting the changes pushed to his repository took a little while because we had accidentally selected nano as the file editor and I was used to using vi, but in the end we got it to work. Finally, we submitted a pull request from his account which can be found here with the new block. The only other issues we ran into were from communication errors between the two of us. Overall, I think the setup process can't really be improved much; it's already fairly easy.