This is simple. When you defeat the first two dungeon bosses you get a santa Maria from each of them. To defeat Eugene put a santa maria on your two best characters. Put Gre on your team. Put Gre in back and Put Mag and (Chain or Pepper) in front or middle. Use Gre's cheer up heal every one when they are hurt (note: cheer up only works on one ally) Use the weakest hammer attack with Mag. It will still do good damage and it saves TP. Continue to attack and heal and if you die then a santa maria will bring you back.
Double attack
Attack a monster from behind to give your characters two attacks in a row.
Easiest cave
The easiest cave to go to is the Shadow Ruins.
Hammer parts
Go to the Sheol Ruins to get the hammer parts.
Infinite experience
Go to a predetermined dungeon and fight the monsters. If you run out of monsters go up/down a level then come back. If you are hurt exit to town and all your health is recovered and experience points/move points are still with you.
Infinite items
Go to Museville (the second town). Beat one or more pre-determined dungeons, pick a floor with good stuff, get it, then go to town by exiting through the entrance or warp station. When you get back to town go to the same dungeon and the items should still be there. No important items will reappear (upgrade kits, Cyframe parts etc).
Maps
If you search every room in a dungeon, there will be a map in one of them. This is extremely useful if you need to visit a dungeon more than once.
More Item space
This isn't really a cheat but try combining a Naolin with another Naolin. This will combine into a Naolin(2). That means it is 2 naolins it one item. It doesn't use them at once and it saves spece. Combine the Naolin(2) with another naolin to make a naolin(3). This also works with Naolin+ and Naolin Gold. I don't know how far you can go but it helps.
Save money
To save money when you have another character and you get to the final floor, switch to Gre and defeat the Boss. Also, Gre has the power to make the Boss wait longer.
Spray parts
Go to the Shade Ruins to get the spray parts.
Top Hunter Mode
To get Top Hunter Mode, play the game a second time. Read the sign next to The Tower of Dispear. If you beat all of your foes, you get the Top Hunter Gear. It acts as a Cyframe.
Unlimited Naolin Gold
On the carrier where you fight Eugene is a room with a soldier lying on the bed. The window on the door has a red cross on it. Approach the shelf towards the back of the room and you will get a Naolin Gold each time that you talk to it. On the 15th floor of the Society Dungeon is a room with three pillars that you can knock down with Mag's hand. Near the wall is a box that contains Naolin Gold every time you enter the dungeon.