Questions on local clone and push back

Hi, I have the following use case - I have a set of files that are used for various adhoc projects, each project is in its own directory, and the files sometime need to be customized/enhanced for a specific project. Ideally some of these enhancements should be merged to a "central" place. I realize that this is not the most optimal setup for software development, however these aren't software projects per se and this setup works very well. To this end, I am thinking of creating a git repository in one directory (central location), then cloning it (-l -n -s) into another directory in hopes of making enhancements there and eventually pushing / merging some of those enhancements back to the central location.

Questions: 1) is this a good approach to achieving what I need 2) I was
getting an error when I tied to run "git push" about the branch being
checked out and 3) how do I selectively push / merge only certain commits
back to the "source" repository / branch?

I am using pushing / merging interchangeably because I don't know which action is more appropriate in this situation.

This is my first time using git so any insights would be much appreciated. TIA