Quantum materials are solids where electrons act collectively to create new phenomena, including nontrivial band topology, magnetism, and superconductivity that advance fundamental science and could power future technologies. Many of these systems exhibit competing orders, where delicate balances among energy scales give rise to rich behaviors and novel excitations. In this talk, I will discuss how these energy scales, band structures and electron correlations can be tuned through structural design, chemical substitution, and external controls such as pressure and magnetic fields to realize new quantum phases. I will present our recent work on tuning magnetic and topological properties in the MnBi2nTe3n+1 family and engineering complex magnetism and its interplay with charge transport in the EuAg4X2 family. Together, these results highlight how small changes at the atomic scale can lead to profoundly different quantum behaviors.