[1] Gajić started his professional career with Napredak Kruševac, together with Predrag Pavlović and Nikola Mitrović.

He scored the opener in a 1–1 home draw with Milan on 8 December 2009.

[2] In the 2011 winter transfer window, Gajić was loaned to Grasshoppers.

On 14 May 2024, FC Vaduz announced his retirement from professional football.

[3] He was playing for the Liechtensteiner club for seven years, from 2017 until 2024, featuring in over 200 games.