Here are my past role jobs from 2.0 to 6.0

Tanks: WAR -> WAR -> PLD -> GNB --> GNB!
(the overall flow of GNB seems to stay the same so I'm definitely not switching)

Healers: SCH -> AST -> WHM -> AST --> SGE!
(I do have a tradition of starting an expansion and relic with a new job so sage it definitely is but not sure if it will surpass AST for me in terms of playstyle - we shall see)

Melee: MNK -> MNK -> SAM -> DRG --> MNK!
(unless the new blitz mechanic fails to impress, might play DRG again as its 5.x playstyle and coolness is incredible. Sadly SAM fell off hard due to its button bloat)

Casters: SMN -> SMN -> SMN -> SMN --> SMN!
(very easy choice seeing my starter class finally becoming a real summoner - this MAY be my main main job at level 90 while rocking the Apocalypse Zeta - my first relic ever - RDM is close second)

Ranged: BRD -> MCH -> MCH -> DNC --> MCH!
(bit undecided on this but I always loved the Edgar references in the current machinist and we'll get freaking chainsaw now! Dancer is just incredibly strong in lower levels so I'm currently defaulting to it during lower level roulettes)


so ultimately: SGE -> SMN -> GNB -> MNK to experience all role job quests first then level the rest. I like all changes they introduced so far very much on all jobs so it's hard to decide which one to play next