When to Use Encryption When Developing for Mobile Devices?

I'm studying and assembling projects for mobile devices, and I always come across dozens of data transmission, some important others do not

1) I would like to know if it is convenient to encrypt all the data I saved in sqlite

2) In code, the time I load the function Can I encrypt there, or only at the time I set the values, would do the conversion and send it to the bank?

If possible I would like some tips on how to do it in an efficient way and if I really should do it.

ex: I have the following function to insert users into the bank I encrypt at the time of converting and do the insertion? What if I want to display the bank's data in a list? I decrypt the same way, I say in the same situation as in the insert?

 public void Cadastrar(){
 final EditText etid = (EditText) dialog.findViewById(R.id.etid);
        final EditText etnome = (EditText)dialog.findViewById(R.id.etnome);
        final EditText etusuario = (EditText) dialog.findViewById(R.id.etusuario);
        final EditText etsenha = (EditText) dialog.findViewById(R.id.etsenha);
        final EditText etemail = (EditText)dialog.findViewById(R.id.etemail);

 nome = etnome.getText().toString();
                email = etemail.getText().toString();
                usuarios = etusuario.getText().toString();
                senha = etsenha.getText().toString();
                id_tipo = etid.getText().toString();
                u = new Usuarios_Model();

                u.setNome(nome);
                u.setEmail(email);
                u.setSenha(senha);
                u.setUsuario(usuarios);
                u.setTipo_usuario(tipo);
                u.setId(Integer.parseInt(id_tipo));
                List<Usuarios_Model> ls = new ArrayList<>();

                ls.add(u);

                new DAO_usuario().Insert(ls);

}

Note: I'm studying PBKDF2, I've been able to set up simple examples, but I have a project that I would like to put encryption on it