I've got talents, you've got talents, we've all got one area or another in which we're experts. Perhaps you're an expert home beer brewer and have an idea for an application that allows home brewers to track the brewing process through their device. Also consider other passions and hobbies, and create an application to fit that niche. Using ideas that genuinely interest you is a great way to get into Android development. You'll find that, by using your own visionary talent and ideas, the end result (the application) will be much more polished and refined than if you were writing an application to track your monthly expenses (unless that is your passion).