A photo portfolio should be a collection of your absolute best work. In nearly every instance, your motto should be "less is more." Every single image should be unique and impactful. Ideally, you only want one picture of each shoot - avoid having multiple images that feature the same scene or model.
There are exceptions, however. For example, a wedding or event photographer might want photo galleries that show what complete sets of photos look like. Likewise, a commercial photographer might want a photo gallery highlighting the final set of iamges they delivered to a client. These would be in addition to the photographer's primary portfolio gallery.