Professional editors never had it this easy. Natural sound, such as the ocean, can be picked up from one clip and put on another. Audio may also come from a outside source, such as music. You can also add narration with the iMac DV's built-in microphone. Working with audio will open your mind to further possibilities.
Most films use a combination of dialog, music, and natural sound.
Hollywood films also use faked sound effects from footsteps to monster screams. Even silence can be effective. Once your basic sequences are pleasing, you can experiment with transitions and titles. These take time to render and download, so be kind to your audience. Keep those silly wipes to a minimum.