The electronic and band structures of the Gd- and Sb-based intermetallic materials have been explored using the theoretical ab initio approach, accounting for strong electron correlations of the Gd-4f electrons. Some of these compounds are being actively investigated because of topological features in these quantum materials. Five compounds were investigated theoretically in this work to demonstrate the variety of electronic properties in the Gd-Sb-based family: GdSb, GdNiSb, Gd4Sb3, GdSbS2O, and GdSb2. The GdSb compound is a semimetal with the topological nonsymmetric electron pocket along the high-symmetry points Gamma-X-W, and hole pockets along the L-Gamma-X path. Our calculations show that the addition of nickel to the system results in the energy gap, and we obtained a semiconductor with indirect gap of 0.38 eV for the GdNiSb intermetallic compound. However, a quite different electronic structure has been found in the chemical composition Gd4Sb3; this compound is a half-metal with the energy gap of 0.67 eV only in the minority spin projection. The molecular GdSbS2O compound with S and O in it is found to be a semiconductor with a small indirect gap. The GdSb2 intermetallic compound is found to have a metallic state in the electronic structure; remarkably, the band structure of GdSb2 has a Dirac-cone-like feature near the Fermi energy between high-symmetry points CYRILLIC CAPITAL LETTER GHE and S, and these two Dirac cones are split by spin-orbit coupling. Thus, studying the electronic and band structure of several reported and new Gd-Sb compounds revealed a variety of the semimetallic, half-metallic, semiconducting, or metallic states, as well topological features in some of them. The latter can lead to outstanding transport and magnetic properties, such as a large magnetoresistance, which makes Gd-Sb-based materials very promising for applications.