A portfolio is an organized, visual collection of a person's progress, achievements, and efforts that demonstrates his/her accomplishments. The collection is a marketing tool aimed at potential employers that includes work samples and personal feedback on them.
Some of the important things to keep in mind are
Convey necessary details like your skills and abilities.
Affirm the above with relevant experience.
Display examples of work in each area of importance like photos, illustrations and videos.
Include your resume.
Show your personality and style.