Gate problems

Trying to get this gate to sit level and swing freely. I used an adjust-a-gate kit. The width is 92", height is 6'. I have used the lightest possible wood, and I can't get this damn thing to hang straight. The turnbuckle that came with it bent straight and came flying out of the holes, so I used a different one I had on hand. Clearly the wheel isn't doing anything except causing the gate to warp since it isn't centered under the weight.

I want to add a diagonal cross brace from the bottom hinge to the top corner, but I'm not sure how exactly to do it with the 3 horizontal boards.

I'm also considered replacing the hinges with 3 extra long strap hinges, one on each horizontal board.

What do you guys think?

Gates