Leve's are best for solo. Group'd leves are better because bonus to exp from leve links.

Company leves are really good exp. Take a bit to complete, longer then a regional leve, but yields good exp.

Prolly the best way to exp is get a exp party. Fast, non-stop, chaining on higher level mobs, usually yields the best exp per hour. There are most likely tons of spots that you can basically camp at now-a-days with the respawn rate being fairly high on mobs.

I haven't exp'd battle jobs in a long time so im not entirely too sure exaclty. I would experiment and what not.