Make What You Want and Let Friends Be Your First Audience
Because friends often share your tastes, building for yourself can also give you a first audience.

paulgraham.com · How to Do Great WorkPaul Graham, the writer of the essay on doing great work, advises people who build things for others to start with their own wants and tastes.
The logic is practical. You need to be sure other people want what you make, and his advice is to start by making what you yourself want. Because friends often share your interests, they can form a ready early audience and show whether the idea holds up for them.
As Graham puts it, "Write the story you want to read; build the tool you want to use." He ties that to excitement: "Obviously the most exciting story to write will be the one you want to read."
He says so many people get this wrong by aiming at a fancier audience that exists mostly in their heads. He calls that choice a mistake.
To try it, make the version you would pick for yourself, then share it with a few friends with similar interests. If they use it, read it through, or ask for more, you have an early sign that the idea reaches beyond you.
Questions people ask
How many friends do I need to test the idea?
A few is enough for a start. Watch what they do rather than what they say, and look for use, rereading, or requests for more. Polite praise alone is not much of a signal.
What if what I want is too strange and no one else wants it?
That can be fine, since odd and strong interests can keep you working longer. Share early and see whether friends with nearby interests respond. If no one else cares, you may need to adjust.
What if my friends are just being nice?
That happens. Friends may compliment you to be kind, so pay more attention to whether they return on their own. If they do not, revise the work rather than asking for more compliments.