We propose a simple unified method for theoretical description of free and bound to impurity neutral and charged excitons, confined in a heterostructure with ring-like geometry. In order to assess the experimentally relevant domain of parameters, we adopt a model of a narrow ring, when for both neutral and charged excitons 3D wave functions can be separated. By using the Fourier series method, we have calculated the energy spectra of excitons complexes in a quantum ring as a function of the electron-to-hole mass ratio, and the magnetic field strength. The size-dependent magnetic oscillations of energy levels of excitons' complexes spectra have been revealed.