Startup. In what sequence to introduce a new social service?

Question

Startups

Hello Habr.
My friend and I are two former developers who moved away from IT towards management more than two years ago (Gods forgive us). Nevertheless, the desire to "create" in the information direction has not yet faded away. We have a great idea for a new social service that we would like to bring to life. And if 5 years ago, it was enough to make a web resource for this, now we need applications in Appsore, Google Play, for a tablet, for a smartphone, etc. We do not want to take on the development ourselves, because the functionality will have to include the ability to conduct financial transactions in the application and work with SMS - we are afraid that we will not be able to cope on our own (there is no experience in developing for mobile platforms). We want to hire third-party developers. But, the budget is limited, and we cannot afford the development of a dozen applications for different platforms. Hence the question arose: where to begin? Website, Apple/Android App with simple interface, only Apple with native interface or what?
Please suggest what should be done in this case and in what order should development and implementation be carried out? I do not want, for example, after the launch of the site to see 10 applications with similar services.
The scale of the project... Something like this (not advertising). An old, but very dear to my heart social network. The target audience is female (18-28 years old), designers, people of creative professions.

Answer 1

(facepalm)
wrote a long comment and accidentally rebooted the computer.
and yes, let there be an opportunity to save drafts here!

Answer 2

aplle - they are more solvent