I know the thread is old, but if anyone stumbles upon this thread looking for help..
At least in April 2021, consider learning Flutter.
You should have Android Studio + Android Emulator. Having a Mac helps a lot if you want to cater towards iOS.
There is a lot of resources over at r/FlutterDev and on youtube and there is a large deeksword community.
If you are new to programming, Flutter uses Dart which is basically Java and Javascript having a baby together.
It's really easy to pick up but you should know basic Software Engineering so you don't do things incorrectly, but naturally you should make mistakes and errors, thats the only way you will learn.