let me add my opinion and experience. Sliding gate if made with thin frame (called 'haddi' in welder's language) and is made to slide on a very thin diameter rod and is out of alignment, it will surely be a headache of lifetime.
Spend some time on finding good fabricator and ask him to show his finished work installed at few houses. Slide the gate numerous time, check width of frame and diameter of sliding base rod.
Rest Tajammal bhai will guide u more.