A learning portfolio can begin with one small project. Explain who it is for and the problem it addresses. A simple landing page, a short edited clip, a poster or a tidy data summary can each show a useful skill when its purpose is clear.
Keep a short record of your process: the constraints, alternatives and the reason behind your final choice. Include what you would improve next. This makes the project easier to discuss and avoids presenting unfinished practice as commissioned client work.
Use material you own or have permission to use. Remove personal information, credentials and confidential files before sharing your work.