Possible Technical Roadmap and thoughts on a startup

Overview:  A friend of mine's son has recently built a web site, and it looks impressive, and we started discussing his project, this turned into a detailed technical conversation to everyone's horror at a BBQ.  This chap is 14, and all I can say is wow.  All hosted and built without spending any money.  I interview many developers, and his knowledge is outstanding.  

I've drawn his architectural explanation below, added a few items to check and what my next piece would be.

Clarification of High Level Design

Thoughts:

1. Build the Native mobile apps, getting users buy-in with a Native App will be considerably higher.  As you have used React, use React Native (React is separate to React Native, a completely new codebase).
2. Cordova/PhoneGap is a wrapper that would allow you to keep a single code base and merely inject the existing code into Native wrappers for iPhone and Android.  As your app is HTML 5, and already looks like a modern mobile app, I'd use PhoneGap.  At least try it out and see if it fits.  You'd then only have to deal with a single code base to update all the platforms.  You could always use Google's Flutter if you wanted a single code base for the web site and Mobile native apps. 
3. Ensure your API's are OpenAPI/Swagger
4. Security - the API already has some protection.  Ensure the database is protected/secured.

Revenue model:  Ads (Gambling Ads pay well). Make a premium-paid for service (keep end-user usage/sign-up free).  Sign-up and collection of money while not directly applicable to this venture, can be done and kept dead simple using Shopify.

Flutter vs Xamarin vs React Native vs PhoneGap

Overview:  As a solution architect and CTO I need to choose the right approach to help our clients select the correct technology and approach to delivering solutions.

Flutter vs React Native vs Xamarin

My History of Building Mobile Applications:

• Originally, building mobile apps required building two code bases generally for Android and iOS in their own language.  Xamarin also allows you to write in C# for a specific platform.
• Next came a single code base that compiled down into each native platform (Droid and iOS), then we would customize for each platform.
• I like Xamarin Forms as I want native apps with a single code base (C#).  One can also write separate code bases for each of the 2 main mobile platforms. 
• React Native is built using Facebook's ReactJS library.  React Native like Xamarin Forms uses a single code base that compiles a iOS and a Android app.

• Note: An alternative around this time was to use HTML5 with PhoneGap and deploy to both mobile platforms, native controls could be used but this was once again a split in the code base.

• Flutter is the newest of the options.  Flutter is from Google and uses it's own DART language, it then can be compiled into various formats including iOS and Android.  Flutter goes back to the single code base that pushes native apps to multiple platforms.  Including the Web.  It is fast, looks good, great native interaction.

More Info: 

Flutter vs React Native - 

Alex Zubkov - 6Aug 2020

Mobile Platform Development for SharePoint 2016

Overview:  There are various options for building Mobile applications.  The simplest answer is to have a fully responsive designed web page and mobile users interact with the application using the mobile devices browser. Another option is to write code for each platform so for example write and iOS application what would be loaded in the AppStore, this requires multiple source codes to be maintained.  An improvement on this approach is to use a tool that creates a version from a single source for multiple stores.  So write once deploy to MS, Android and Apples store; PhoneGap and Xamarin are examples.

Xamarin uses C# code and compiles executable applications for each target mobile store such as iOS, Windows and Android.  Xamerin uses it's own IDE or a add-in for Visual Studio.

PhoneGap is also refereed to as Cordova.  PhoneGap creates the web application using HTML5, CSS & JS and wraps this web application in a plaform control/container.  In effect, the html page is hosted in each platforms executable within a web control.  The exe can interact with the web pages:  

Unity is another development platform probably the 3rd biggest and generally favored for gaming.

Summary:  Responsive Web Design works on the mobile device as a native html app using the mobile browser.  If you need to interact with he phones features and you need to write an application for the platforms store, rather use Cordova/PhoneGap where you write once and distribute to each desired platform.

Updated: 29 August 2016
More Info:
http://magenic.com/documents/Xamarin_PhoneGap_eBook.pdf?EBookTest