Significant emphasis has recently been placed on developing innovative methods to harness green and sustainable energy sources. For instance, light-driven photocatalytic water reduction, resulting in the production of molecular hydrogen has demonstrated its ability to offer solutions to the ever-growing global energy demand However, for this to become a reliable building block of a sustainable economy, research must address the challenge of environmentally friendly hydrogen production. Photocatalytic reactions involving transition metal complexes are a possible and perhaps viable method in this respect. However, these systems come with problems of their own, centered around low yields, unsatisfactory stability, and the low abundance of rare earth materials often contained in the high-potential molecular systems. In particular, replacing rare-earth materials with more readily available first-row transition metals has become a central challenge in both theoretical and experimental work. But, first-row transition metals have a significantly altered electronic structure as compared to the successful systems containing Ruthenium or Iridium. The understanding of the implications for photophysical and photochemical processes is just emerging. In the case of transition metal complexes, commonly employed levels of theory are pushed to their limits. Wavefunction-based methods, such as Complete Active Space Self-Consistent Field (CASSCF), come at high computational costs, due to the large number of electrons one has to correlate. Density Functional Theory (DFT), on the other hand, lacks in many cases the necessary accuracy and shows a strong dependence on the functional and the type of electronic transition. Altogether, this increases the demand for new methods that are computationally inexpensive yet accurate enough to effectively describe these systems.