This post isn’t about the nitty gritty questions of what formats and how many pieces should be in a portfolio, this is about what content you should have in your portfolio. Because your portfolio is your shop window display. If you’re not showing your best work out front, you’re not going to get people deeper into your store. And you don’t put everything in your window display — just the things that are going to attract the kinds of clientele you want.
Whether you work in illustration or gallery or concept art, the fact remains that you make a name for yourself by doing something better than anyone else can. Sure, there are artists that exist by being the “second best” at something or “the poor man’s version” of someone else, but it’s infinitely better to have a style all your own. By “style” I mean the combination of medium, technique, and voice that makes your artwork yours.