Reset the game repeatedly until your main characte - ither Claude or Ren - as Dexterity. Play the game as normal until after Cross, when you have Celine and get the mission to go to the cave. Get Sensibility 1 and 2, from Cross and Herlie.
Level up until you can survive one battle in Lasguss, north of Cross, and then run around and level up there until you have 40000 fol, resting as often as you have t - ventually this will be easy, but don't progress with the plot until then. Sense 2 has playfulness on it, and leveling up perseverance to 10 and then playfulness to 10 gets you a grip of cash.
On your main dude, level up Courage and Poker Face until your Pickpocket skill is 9 or 10.
When you have the money, buy the Bandit Glove in Herlie. Save your game, then go into Clik BEFORE IT IS DESTROYED in a private action. Watch the event where Filia predicts the town's doom, and pickpocket her to get the Mischief. This accessory tosses crap at you the entire game, including cash and little trinkets that give you free levels. It is amazing and wonderful.
Then, go to Mars, and save outside. Go in in a PA again, and go to the east side of town, and pickpocket the Treasure Chest from the old man. This gives you three random items, and you can reset until you get, among other things, the Marvel Sword, which gives some ridiculous attack power and will carry you for a very long time.
At Lacour, be SURE to get to the very last round of the tournament, against Dias. Then, get the Sharp Edge after the battle with him from the dude who sponsored you. You can customize it with a mithril, and then the resulting crappy sword with another mithril to make the second strongest sword in the game, which also craps out an extra AE attack, which is utterly amazing.
Get Opera instead of Ashton. Do not even start or do anything related to Ashton, he is worthless. Use her Machinery skill until you make the White System, and learn Healing Star with it. Use it nonstop until you manage 999 proficiency in it. It heals far more, far more quickly, and for far less MP than any magic healer can do, with almost no effort, and lets you use Opera and 3 other good characters, instead of weighing your party down with Rena or some other caster, all of whom are worthless.