How To Decide What To Build
When a startup launches, there have to be at least some users who really need what they're making — not just people who could see themselves using it one day, but who want it urgently. Usually this initial group of users is small, for the simple reason that if there were something that large numbers of people urgently needed and that could be built... See more
paulgraham.com • How to Get Startup Ideas
The concept is pretty self-explanatory: Build the smallest thing you possibly can in order to get meaningful feedback on your idea.
Andy Budd • The Growth Equation: How Early Stage Startups Can Build a Powerful Engine for Growth
So keep your project small as long as you can. And don’t allocate too much money at the start.