This post on the Unreal Engine blog presents 6 short stories on how ot fund your indie game project. All of the hint at the value of a working prototype, of asking for and listening to feedback, of using that feedback in some way, either responding and expanding or for analytical introspection of your project. Look for attention, look for interest, listen to the responses, respond honestly while respecting your vision.
Keeping the team as small and costs low for as long as possible.
Reuse whatever you can rather than creating new technologies. That way you'll be investing in realising your vision, the things that are unique to your game, rather than reinventing the building blocks. Build on the shoulders of giants. Along the way, by serendipity or discovery you may invent new, useful, general purpose technologies that are valuable and sellable, (well done if you do).
Make sure you can answer the question; how is your game going to make money?
Building something, even something small but tangible builds confidence and offers immense learning opportunities, both for the team's capabilities and how others perceive the sample.
Look for multiple lines of investment at the appropriate moment. Self-funded, friends and family, public agencies, investors...
https://www.unrealengine.com/en-US/blog/how-to-fund-your-indie-game
