I dunno about 30+ because atm I'm just levelling all classes to 30, but I've just been doing:
0-10: Whatever starting zone you learned the class in
10-15: Summerford Farms
15-20: Aleport
20-30: Quarrymill
I use the grand company seals you get from the fates to just buy weapons for the class for levels 22-30. The armor I've just been sticking them in whatever gear I have that they can wear and I just check every few levels if they can wear something else. Got my chocobo as healer.
Plugins I'm using:
Chanko - Eats food for the 3% buff, just buying 99 flatbread for cheap and letting it use those.
ChocoboCompanionStanceDancer - Sets chocobo stances based on health
LightPatrol - Attacks shit around you when no fates are up
Zekken - Dodges telegraphed spells
It's all working fine so far pretty much. Once I get everything to 30 I'll get everything to 40 etc. I don't even have a class over 30 lol I levelled rogue manually to 30 which is why I'm only botting things up to 30 because none will get the exp buff after that. Might just spam dungeons on one of the tanks to hit 40 then fate everything up to 40 and so on.