I would stay self funded as long as possible. Then move to testing the prototype with customers. If you merge the results from experts and the customers then you have a high chance to presenting to investors and share the data. Im available to talk more and help in anyway possible.

You can start by having a text to download sign up on your website. I use Link Texting. You can also create a landing page that can build a email listing so that you can send emails to people who are interested in your app features. Read a article by Kevin Kelly called 1,000 True Fans.

I would reach out to developers on LinkedIN or post a question on Quora. Or if you have specific needs I would be willing to set up a call and talk to you about app store optimization.