Hoenn's 8th gym puzzle can be frustrating to solve since its purely by process of trial and error, and the player is forced to start from the beginning if there's a mistake at any given point. So, I've decided to document and post the path in the forum so new players don't have to waste a long to figuring it out! 
Fig.1 : Puzzle Solutions Part 1 and Part 2.
Fig.2 : Puzzle Solutions Part 3.
Fig.1 : Puzzle Solutions Part 1 and Part 2.
Fig.2 : Puzzle Solutions Part 3.