So far I have just messed around with the designs that it comes with. There are other packs of themed fonts and squiggles that you can purchase or add for free. If you are using it professionally, naturally make choices within your brand's color story and style and keep everything very readable. Stay away from adding diamonds and moustaches to every picture for example, unless you sell diamond encrusted moustaches.
Choose your photos in the order you want them to go as there isn't any drag and drop rearranging of the order. But you can duplicate an image for it to last longer. Once you have your images chosen the app sets the length of each photo to fit in either a 15 or 30 second clip. You can add a title to the beginning. For a small one time fee you can remove the Flipagram watermark and replace it with your own name at the bottom.
If you have music on your device you can insert that. You can narrate a voice over. Or they offer previews of popular songs that you can use without any copyright issues.
Although I have spent several hours figuring out how to get the look I want from these programs, they are remarkably intuitive and fun. When I would start to get frustrated with their quirks or limitations I would remind myself that I was creating professional materials for myself with technology I already own. What a powerful feeling to have these tools at my fingertips.
I hope you have fun exploring these apps. Let me know if you have any favorites I should try.