How to make your app responsive?

For developing a phonegap Framework7 app for iOS and Android, both tablet and smartphones,
what should I do to make it responsive? To make font size responsive? To make icons and padding and margins responsive? To make the whole UI/UX responsive easily?

Nothing.
In tablet use multi views.

shastox right, for simple projects use multi views, for large projects you can use HTML responsive

Framework7 is already optimizied to be used on responsive devices. Usually you shouldn’t do anything about this:

If you open same app on iPhone and iPad you will see that UI elements and font sizes is same, there is just more content fits to larget iPad screen. If you want to increase everything for iPad, then there is no sense in it.

For other stuff, just use CSS media queries https://developer.mozilla.org/docs/Web/CSS/Media_Queries/Using_media_queries

What is multi-view???

Doc
Simple template with multi-view