Defects and impurities strongly dictate the physical properties of materials by tuning conductivity, modulating magnetic response, and changing optical properties. Here we analyze how these entities behave in the prototype quantum material ${\mathrm{FeGa}}_{3}$. We have studied its intrinsic defects (vacancies, antisites, and interstitials) as well as different types of dopants such as Zn, Mn, Ge, Co, In, and Ru. Intrinsic defects are shown to have large formation energies, whereas dopants have a larger solubility. Different electronic and magnetic states, including localized polarons, were found to be induced by specific defect charge states, significantly altering the properties of the host material.