A method to create compositionally disordered compounds with a high number of cations in the matrices, that utilize the cubic spatial symmetry of the garnet-type crystalline systems is demonstrated. Mixtures of the garnet-type powdered materials solely doped with Ce were used to create atomic compositions of high complexity. Several mixed systems, namely Gd3Al2Ga3O12/(Gd,Y)3Al2Ga3O12, Y3Al5O12/Gd3Al2Ga3O12, and Y3Al5O12/Y3Al2Ga3O12 were annealed, compacted and sintered in air. The materials were evaluated for structural, luminescence, and scintillation properties. It was demonstrated that the properties of the resulting ceramics are a little dependent on the granularity of powders when the median particle size is below ~5 μm.