First you need to show there's a market, no one invests in anything unless they think it will get big. So you release a basic MVP (minimum viable product) to show the basic features and get people interested, doesn't have to be optimised, doesn't have to support all the platform you're aiming at, just something that works.
Maybe B4X forums should have an investors section? We have the business section, so I guess that could cover this, but that tends to be more for part time or one off work.