Lights at Deep Dungeon-At Deep dungeon you can make light by killing your enemies and letting them turn into crystals, however chests don't do anything so....
Copy Items-Give the 2 swords ability(ninja) to anyone and equip a shield in their right hand and the item you want dupicated in their left hand, go to any shop and choose best fit, buy it, now you should have whatever item you wanted double. It costs a bit of money but hey, you get way too much money in that game anyway.
Easy Level up and Job Points-Give any character Accumulate(or if the character doesn't have the squire job use Chakra from the Monk Job) go into battle and use the ability over and over, you should get LOTS of experience or job points, but if you use chakra you need to have your magic or hit points down to get experience or job points. It may be slow but think about how long it would take to do it normally.
Raise Brave Permenantly-Use any ability that raises brave and it will permenantly raise it by 1 point. Then exact negative works too, if you use one that lowers brave points it will go down permenantly.
Best Summon-At the Deep Dungeon on the Bottom floor Is a boss, if you have a summoner and get hit by it(hope you survive) then you can learn it, but make sure to get as many summoners as you can, because you can only fight him once.