In this article, we report the various changes observed and studied experimentally and theoretically in the structural, magnetic, and thermodynamic properties of the Gd2-xNixIn (0≤ x≤ 1) intermetallic compounds owing to the changes in the composition of Ni substitution. The compound Gd1.6Ni0.4In have many successive transitions with T_N ≈ 102 K, T_t ≈ 145 K, and T_C ≈ 86 K, 190 K which are of second-order and seem to be a mixture of phase transitions of compounds Gd2In, GdNiIn, and some other compounds from the RENiIn (RE = Rare earth) family. Similar transitions have also been observed with smaller magnetic moments in other compounds from the system. The curves of Curie-Weiss temperature (θ_P) and effective magnetic moment (μ_eff ) for the changes in Ni composition show declination at specific values. The critical analysis of the compounds with values of x = 0.4, 0.6 finds it difficult to distinguish among the best fit theoretical models of critical exponents. Theoretical analysis using density functional theory is also in good agreement with the experimental findings confirming that Gd is the major factor of magnetism in these compounds.