The optimal platforms for Ren'Py are Linux and Windows. Therefore, it's better to have an inexpensive Linux device for gaming than an Android device. Even saving games on Android is problematic.
To transfer saves, you can either manually transfer save files using a file manager or Google Drive, or save them using the Ren'Py service (though this may not work in some regions), which is accessible from the loading and saving screens within the game.