What outreach resources did you go through and how did you target potential users once you had a prototype?
edit (from comment I posted):
Some friends and I had trouble getting leads on who to "sell" our prototype to, and we had the thought that this may be an even more legitimate problem than the one we were previously trying to solve.
Is this a problem that other startups have faced, trying to find specific (with contact information) customers to talk to and become the first users?
By the time, I launched MVP, influentials in the domain were aware of me. In a few months since launch, I gained several hundred registered users through these activities ... not a single penny spent on ads or to generate traffic.
Now I am working on figuring out how to generate revenue ...