There are a couple of ways to learn Lua – Corona for app design. I recommend browsing and trying out some tutorials then starting straight in to the app you are going to make.
Consider how it is going to look. How many “scenes” will there be? Will it send/store information to the cloud? Will it interact with the device – camera/memory/gps/maps???
http://coronalabs.com/resources/tutorials/images-audio-video-animation/