Błędnie: Jim is so conceited- he thinks he deserves gratification for any extra job he does because according to him no one else can do it. Poprawnie: Jim is so conceited- he thinks he deserves gratuity for any extra job he does because according to him no one else can do it.
"Gratyfikacja" to 'gratuity' albo 'ex gratia payment'. 'Gratification' to "zadowolenie, satysfakcja".