The work in your portfolio needs to look real. Even if you made it up. It doesn't matter if you didn't actually work with the Crest client and got that ad produced in real life, your work needs to look like it could.
|real real ad from Oct 2013|
It's kinda like how gymnasts don't show that they can do cartwheels when they go to tryouts - they go all out and show the amazing flippy-jumpy-twisty things they can do. Everybody knows they can cartwheel.
You want to be able to do that basic stuff, of course, you'll have to do them when you get hired.
But, in order to get hired, you have to show them the flippy-jumpy-twisty things you can do first. You can do banners and emails for sure - but make sure they're above-and-beyond basic and show lots of creativity and strategy.
Here are some examples of flippy-jumpy-twisty things* from some recent Creative Circus grads
(*I should probably research what gymnasts do, shouldn't I?)
How do you get here? Start by reading this: The Epic Portfolio Post.