You have ideas you want to build or maybe you are looking for ideas.
What’s more important than the idea in my opinion is the WHO are you serving with the idea.
For example do you want to build an app for pet owners? designers? bloggers? business owners?
Why does that matter?
Because you will be talking and working with them a lot, and you need to like them and their industry or else you can’t last long.
Just because you have a good idea that solves a real problem doesn’t mean you can pull it off unless you can work with the market, they like you and you like them.
That's right, the first question is "Who?".