How experienced are you? If you are good with cards already, I would recommend including something like "Cradle to Grave" by De'vo, as well as demonstrating the different types of motions that are possible with cards (fans, spreads, springs, card shots, etc), ending with something magical that takes the audience by surprise and leaves them with a more mystical feeling while also being impressed by the displays of skill.
That kind of thing drives people nuts. They love it.
If you're less experienced, I would still advise creating a routine that offers a broad mix of flourish types. If you can end it magically, or work magic into the act, the audience will love it. Sometimes it's difficult to entertain an audience with nothing but flourishing. However, it's possible!
You can weave a historical narrative into it, demonstrating card handling / flourishing methods through the ages as you speak. Taking it up to the present day, and ending (again) with something magical that completely disarms them, that they weren't expecting.
Just some ideas. Good luck, my friend!
All the best,
Vinnie