The only advice I can give about leveling all Jobs is to do it in sets of 10, like say you have all Tanks at like 60-ish, you shouldn't take PLD to 100, then pick up DRK, you take PLD to 70, then you switch to one of the others and take that to 70, then repeat until all 4 are 70, then you continues all to 80, so on, it will make gear management overwhelmingly simpler, since you can just throw away all the level 60 gear that you don't intend to keep for glam purposes once every relevant Job is 70. Trying to take any given Job to max(besides your main) before switching will only cause problems.