Inventory management is a huge pain, I agree. That is, while leveling your classes. You dont want to toss out the gear because itll help your other classes but then organizing everything by level, knowing when its time to upgrade, or even going back to the retainer to do so is a pain. In the end I just decided to screw everything and just level each class completely separate from each other. No hand-me-downs. They each start with the race starter gear, and go from there.

The ONLY classes that I keep gear for is DoH and DoL which I try to keep a set for every 5 level bracket. They each use the same gear minus the tools, its much easier to keep track of two sets rather than 6(?). And most importantly, while you can always just do dungeons or even leves to get more combat gear, crafter gear is much harder to come by unless you want to just buy everything. Or level every crafting profession at the same time, not recommended unless you like managing hundreds of crafting mats.

As for actually leveling I actually find it much faster to level with leve's, FATES, and dungeons than going through the whole quest story line. Grab your leve's in town and do every FATE that pops up near you as you wait for duty finder to pop. Great time for ranking up your chocobo too.