Many technologically relevant transition metal oxides for advanced energy storage and catalysis feature reduced transition metal (TM) oxides and are often nontrivial to prepare because of the need to control the reducing nature of the atmosphere in which they are synthesized. In this work, we show that an ab initio predictive synthesis strategy can be used to produce multiple gram-scale products of various MgVxOy-type phases (δ-MgV2O5, spinel MgV2O4, and MgVO3) containing V3+ or V4+ relevant for Mg-ion battery cathodes. Characterization of these phases using 25Mg solid-state NMR spectroscopy illustrates the potential of 25Mg NMR for studying reversible magnesiation and local charge distributions. Rotor-Assisted Population Transfer is used as a much needed signal-to-noise enhancement technique. The ab initio guided synthesis approach is seen as a step forward towards a predictive synthesis strategy for targeting specific complex TM oxides with variable oxidation states of technological importance.