Portfolios are assembled to show finished work. The people reviewing them are trying to answer a different question: what would it be like to work with you.
What reviewers actually do
Spend a short time. Scan for something that stands out, then look more closely at one thing if something does.
That means the first item matters disproportionately and the quantity matters very little.
Show the reasoning
A finished result shows you can produce a finished result. A short explanation of the problem, the constraints, what you tried, what did not work and why you chose what you chose shows how you think.
The second is what a hiring decision actually rests on.
Fewer, better
Three pieces with proper explanation beat twenty thumbnails. Anything you would not want to discuss should not be there, because you will be asked about it.
Show your own contribution
Team work is normal and unclear attribution is a problem. Say what you did specifically. Reviewers assume the worst when it is ambiguous.
Make it easy to reach
A link that works without registration, opens quickly, and can be read on a phone. Portfolios behind logins, in large files, or requiring specific software get skipped.
What to include if you have no professional work
Personal projects, treated seriously. Contributions to open work. Detailed write-ups of problems you solved even where the result was not shipped.
The absence of paid work matters less than the absence of evidence you can do the thing.
Keep it current
A portfolio last updated three years ago suggests either nothing recent worth showing or no attention to it. Neither helps.