Careers
What a junior portfolio usually has to show
A junior book is a small set of pieces a reviewer can finish in one sitting. It is not a complete career, and it does not have to look like a reel from a large network.

A common request is a handful of pieces (often fewer than ten) with a short note on each: the brief or the problem, your role, and what was made. If you wrote the line but did not art-direct the layout, say so. If the work was made in a class or as a speculative assignment, label it as student work or as spec. Reviewers can usually tell. The label saves them from treating a fictional client as a live one.
Finished work that ran is useful when you have it, including small jobs. A clearly argued speculative campaign can also be useful if the brief is stated and the constraints are realistic (a medium, a length, a legal line). Decorative mock-ups with no brief are harder to discuss.
Do not pad the book with every exercise. If two pieces make the same point, keep the stronger one. Put the work first and the biography last. A reviewer who has to scroll through a manifesto to reach the first ad has already used up some of the sitting.
This is a description of a common review format, not a rule issued by a trade body, and not a claim about what every hiring manager will ask to see.