There are also some pretty nice leveling tricks you can do with Field Barrier. Equip a chars dragon with Barriermagic, lvl it up to 50 to get 'Field Barrier Lv 3' (This can be helped by buying Barrierhearts from Torippo for medals). After that you can run into every enemy that you have defeated and while you don't get xp you get sp so your dragons will rise in their job lvls which is way more importants then characterlevel anyway.
Then go to Underground Cave, after the Robot City at the end of Laser fields, and run to the end. There you have a road left to a door + savepoint and a road right(behind a blue barrier so make sure you can destroy those) which leads to a room with at least 30 of those onion guys. Run through them with field barrier to get loads of SP (I got 2SP each at lv 40+) and level up any job you want for your dragons. Make sure to level up the 'general' job so you get more skillslots and equipmentslots.
Then run back to the door with the savepoint, enter, go back and voila, the onion guys have returned. Kill them, run back, kill them, run back
Your shadows will become really powerful with just 1-2 hours of running.
note: first time you do it a dragon will spawn but he is easy so kill him and continue.