To level a job, gain Job Points (JP) during battles. Every successful action (attacking, casting a spell, guarding, using an item, etc.) a character executes during a battle will result in JP. The amount of JP granted varies between Jobs from one JobLevel to the next one. On average you can expect to gain 20 JP for each successful action in a turn when your JobLevel is between 1 and 14, and then it drops to between 8 to 20 JP once you are over JobLevel 14. In order to reach the next JobLevel you must accumulate a total of 99 JP. This amounts to over 5 actions per character at first, then up to 13 actions when over JobLevel14. The easiest way to farm JP is to enter one of the starting zones. The level of the monsters you face does not matter. They will not damage you and you can ignore healing for the most part. Once in battle, you Guard with every character between five and twelve turns in a row, then attack with one or two characters and guard with the remaining characters. Make sure to Guard before attacking so that all characters get a successful action.
Go to the Town Of The Ancients and talk to the child two stories up the grass hills. He is back behind the stairs. He will tell you that he will give you a prize if you ride around the continent. Leave town and go east a bit. Get a Chocobo and ride around the outside of the continent. Go back and talk to the child for your rewards. Sell them, then repeat.
Reach at least level 20 and have decent armor. The best place to level up your job is around Ur, dealing with the weakest enemies in the game, Goblins. Have a Bard with a Dream Harp so you do not waste potions or MP. You can reach job level 99 in 98 battles by guarding against this enemy, only receiving 1 point of damage from each attack. During each battle, there is a certain number of times according to the number of actions required to level up a job. For example, a Bard requires 5 actions job level 1 to 14, and 6 actions job level 15 and up. The need to heal is unnecessary, but if desired you can use the Bard's Sing ability every ten battles to remain at maximum HP.
After you get dropped out of the dragon's nest, go to the area with the spring and the gnome. Talk to him and he will give you a Mini. However, you can talk to him again and get one for all of your party members.
The legendary items of Eureka are mainly used by Knight, Ninja, Devout, and Magus. Knights get two legendary items, Excalibur and Ragnarok, equaling a total of 277 attack. Ninjas get the legendary dark sword Masamune. It has 132 attack by itself. White Mages can use, but Devouts use the legendary item Elder Staff. It casts Cura. Black Mages and Magus use Omnirod. It does not cast anything, but when used in melee it inflicts gradual petrification.