Ask HN: Help me design a personal project

I am thinking to start working on a project which in future would become a product (hopefully). I want to take it as opportunity to learn what modern programming era has been shifted to. As of now, All i know is Java based web apps, with old school Business Layer (EJB)/JSP front end. Not to mention, the front end isn't optimized for different platforms and if I have to create web apps out of this then its an other story for me.

So how should i design the app which

1. Will have a Web Client for Administrators and for users 2. Should provide user access on iOS/Android

I was looking at different technologies and I am so confused. There is Angular JS, ROR, DJango, IonicFramework and so many more ... So if i ask you to design a modern web-app for browser and cell phones,

1. How many tiers you would have 2. What framework/would you use at what tier 3. What architecture you would use. I mean there was SOA back in the time and now there is a new buzz word (micro-services). How would you decouple server with front end so that same functionality could be used on client brwoser and native mobile apps.

Any help is appreciated.