Ligands play an important role in the stabilization and functionalization of Au nanostructures and in self-assembled monolayers. Despite the increasing number of organic groups capable of stabilizing gold in addition to the popular thiolate ligands and the emerging alkynyl groups, there has been no systematic comparison of organic ligands regarding their binding strength to gold. To facilitate the future experimental design of promising ligands for gold surfaces, nanostructures, and nanoclusters, we provide a comprehensive view of the ligand-gold interface for six types and 27 ligands from first principles dispersion-corrected density functional theory. We find a surprising contrast between simple and bulky N-heterocyclic carbenes (NHCs). The bulk NHCs benefit from greater van der Waals contributions and additional Au---H-R hydrogen bonds. In fact, we find that alkynyl groups and bulky NHCs demonstrate the strongest binding with the gold surfaces. We further explore the computational design and show the viability of NHC-protected gold nanoclusters of magic stability. The overall trend from the present work not only confirms the emerging role of alkynyl ligands but also predicts the very promising direction of using bulky NHCs to achieve stable gold nanoclusters and interfaces.