I started this a while ago! I'm around level 37 and just got the second mount, the Ibek, so I can finally Jump Good and the map is opening up a lot, so I have some exploration to do. Off the top of my head, maybe going west of the capital is finally not too strong for me. There's the volcano to the SE of the desert, too. And having looked at some guides, the mountains north of the capital are apparently also an option atm. We'll see if I'm forgetting anything.
I started with a warrior, monk, cleric and black mage and have more or less kept those roles the same.
Warrior -> Vanguard -> Reaper. The Bloodbind sword kicks ass already and synergizes extremely well with reaper, and luckily half of reaper's skills are weapon agnostic so I don't need to actually equip a scythe when paired with warrior's secondary skills, I have a full arsenal. I just got my first weapon stronger than bloodbind but luckily only by 5% or so, so I'm keeping the BB for now. I still use warrior's secondary skill because the big hit that normally causes retaliation damage simply doesn't with my lifedrain setup. This is my favorite character setup right now, it's just so satisfying.
Monk -> Fencer -> Monk -> Hunter. The lack of synergy here is kind of frustrating (can't use fencing w/o rapier, can't use monk w/o barehand, can't use hunter w/o bow... right now I have monk secondary on hunter because some of the chi/support skills can still be useful. Hunter does really good damage though and I like their cooldown system more than monk's AP system (I never minded fencer's ap because their moves are all nice and cheap, making them essentially infinite). I might switch them to Ninja at some point since I've unlocked that, but...it's yet another DPS class with no synergy to the previous ones, unless I'm mistaken.
Cleric -> Scholar -> ???. This one is still stuck on scholar because "skills cost less MP" is pretty great as a passive and I don't know what else to do with them right now that both jobs are mastered (well, scholar isn't mastered, but I learned both of the buyable skills so it essentially is). I put them as a warlock for a bit, just long enough to get refresher, but their mind is low enough that damage caster isn't a great path for them regardless. They have a decent attack and spark shine/aero do decent damage, but they exist largely for support. Wondering how to fix that. I guess I can stick them in warlock for a while longer to even out stat gains? I dunno. Maybe I'll just make them a DPS class with secondary white magic or something. Monk? shrug
Wizard -> Shaman -> warlock -> Dervish. Black magic all the way! Shaman was neat but mainly struck me as "slightly expanded black magic," and Dervish...also seems that way, but less squishy. Lifedrain on shaman was pretty good though... Warlock was OK too, but Refresher was really the draw there. I wish I'd gotten it on both my casters sooner. We'll see where Dervish takes us.