The issue I'm having with building a portfolio is I'm unsure how significant an app needs to be before its worth including. I don't have any ideas for apps that

The issue I'm having with building a portfolio is I'm unsure how significant an app needs to be before its worth including. I don't have any ideas for apps that could be a commercial success (and I don't have much desire to be a developer for myself as opposed to being a freelancer). I could just rehash the same to-do list app that seems to be vogue but it seems too simple. Am I overengineering or should I try to make a technically non-trivial app?