Trouble rooting my Samsung Galaxy S Duos 2(gt-s7582)
What package were you using in Odin to flash your phone?  I don't think flashing a new OS in ODIN will help much with rooting.

Download towelroot on your phone, and root that way:  Towelroot.com

Download and install the APK.  Click the lamda, and then install SuperSU from the Play Store.