A simple method is proposed in which basis sets of Gaussian-type functions (GTFs), suitable for relativistic Dirac-Fock-Roothaan (DFR) calculations, are derived from their nonrelativistic analogs. The relativistic basis set is obtained through augmenting the nonrelativistic one by several GTFs determined from relativistic calculations for hydrogen-like atoms. The usefulness and reliability of the method is illustrated by DFR calculations of the ground-state energies of lanthanide and actinide atoms.