Key point
The proof matters
Your repo is the proof, not your notebook screenshot. A reviewer should be able to open it, see the raw files, run your cleaning script, and find the cleaned output and charts.
Keep the project small. Two raw files are enough if you clean them properly and show one join or group result.
What to include
Use a public repository. Put data in clear folders so a classmate or recruiter does not have to guess where things are.
Your repo should show the full path from messy data to usable data: load, inspect, clean, join or group, chart, save.