Looking over the repository, you're still distributing somewhat unnecessary files (namely, King of Thieves/bin/* and King of Thieves/obj/*). Additionally, there are DLL files in your repository which.. is kind of a poor place for them (also, the SDL.dll appears in multiple places).
For dependent packages, like MonoGame, why not use a package manager such as NuGet (disclaimer: not being a .NET dev, I haven't personally used NuGet - there may be others that better suit the needs of the project)? I imagine you're all using Visual Studio primarily for the development environment anyway, so it shouldn't be too difficult to set up.
I'm assuming that the XML files in the bin folder are test maps and such. Which begs the question...why are they in your source hierarchy? I understand why the binaries are there (because Visual Studio defaults to having godawful setups and loves mixing binaries and source code), and there's not a huge need to change that if the directories are ignored anyway, but right now if you were to attempt a release build you'd have to manually copy your game data from the Debug folder to a Release folder before you could test.
I'm guessing that these files are either legacy (and should be deleted), or that they're extra data that's being handled outside of the Content Manager in MonoGame. I recommend setting up a directory within the source tree containing such data (as I assume the Content/ directory exists purely as data that should be handled by the content pipeline at build-time), and then using that directory as the working directory during debug (easy to set up in project settings).