This isn’t what I would recommend. Unfortunately, it’s what the repo recommends, so that makes things rather difficult. Generally, you should be using pip to install packages, not running setup.py directly; however, you’re looking at a fork of the project, and checking out a specific branch, so this is definitely going to be messy. You’re running an unreleased version of someone’s fork of a package. This does not seem like a good place for a Python novice to start!
But the flip side of that is: there’s really no way that the default setup experience can be made better here. Effort has been made to make the normal experience much cleaner, but that’s always been with a focus on using a package manager rather than grabbing the source code and running setup.py. That said, though: you are probably correct that a virtual environment would help; and the best solution here may well be to submit a pull request to the project, suggesting the use of one as part of its setup instructions.