Hey that's great! Go for it.
Here is a great list of judging criteria to keep in mind from pcam:
All contestants are judged by the following criteria:
Appearance of person and act: 10 points
Smoothness of presentation: 10 points
Technical skill: 10 points
Originality of theme/presentation: 20 points
Entertainment value: 30 points
Mystery value: 20 points
For 7 minutes I would aim for 2-3 effects that play well as a routine together. Pick your favorite effect you like to do and build it into a routine. It is not mandatory that it needs to be an original effect, but try to avoid doing the patter out of the box. Once you have some ideas, feel free to pm me and I'd love to help with some feedback if you would like.
Best luck.