Mutliferroic and magnetoelectric gallium ferrite (GaFeO3) is plagued by substantial electrical leakage in polycrystalline form. Here, we report on understanding the conduction mechanism in gallium ferrite ceramic samples vis-a-vis processing conditions. The results show that oxygen annealed samples exhibit minimum electrical leakage as compared to air or nitrogen annealed samples suggesting the role of oxy3gen vacancies on electrical conduction. Detailed time and temperature-dependent impedance spectroscopy analysis of the samples showed higher activation energy of conduction in oxygen annealed samples than in air or nitrogen annealed samples. The lower activation energies of 0.3-0.4 eV in nitrogen/air annealed samples were attributed to higher oxygen vacancy concentration while oxygen annealed samples with low oxygen vacancy concentration exhibited higher activation energy of similar to 0.50 eV (high frequency, i.e., grain) and 0.98 eV (low frequency, i.e., grain boundary), latter due to superior level of oxygenation at the grain boundaries. Further, X-ray photoelectron spectroscopy revealed that the oxygen vacancies are compensated by the valence fluctuation between Fe2+/Fe3+ ions whose extent is higher in air/nitrogen annealed samples than in oxygen annealed samples. The conduction mechanisms that could be active are most likely to be double ionization of oxygen vacancies and hopping from Fe2+ to Fe3+ states, latter especially in oxygen deficient samples.