To start a "New Game+" that allows you to take all of your statistics over with you to a brand new game, complete the entire game once through.
Unlimited Chips & SP
At London city, go to the casino (slum area). Use a save and load method, and play roulette by betting 1000 chips for the first 9-12 numbers which you can earn around 24000-26000 chips if you win. The chances is roughly 1/3 to 1/4. Quit casino and save after you win. Naturally, if you lose, reload your last save. Repeat that and you can earn unlimited casino chips.
After you obtained all the goodies in the casino presents, you can sell that item in casino which recovers 50% of your HP and EP at the shop next door. You can only carry 9 on you at a time. So you will have to buy them from casino using chips and sell them at the shop. You can get 5400 TB for 9 of them. Repeat the step above and you can have unlimited money and unlimited SP because SP can be purchased at the shop.
Omega is the final boss in the holy beast shrine At first it seems impossible to kill Omega with him having 99999 hp and ep but he is rather easy to defeat with a golem that has a special attack that takes a % of damage. I used Sebastian sniper shot. The first few shots with him did about 35000+ damage. Other golems you can use is Raiko or Samurai. Lastly, keep your members out of his God Scream ability if possible.
There are four weapons you can get from the god orbs (one for each of your characters Yuki, Raigar, Karin, Atsuma).
The first you have to get is Atsuma's. Get this when you visit the sge. A part of the story of the game after that there are three more you need to find scattered throughout the game. One sage is right outside the sages' area you just go down the stair case and look around the entire tower -- there will be a golem there. When you kill him you will get its core and a god orb.
Another one is in the desert out side the Junk City in one of the ruins but the doors to it are locked. On the middle right side of the area between the 2 ruined buildings is a sink hole. Go to it and you will fall through there is another golem there who will give you a god orb after you defeat it.
Then there is the area where the Yokahama bridge was blown up. Go down to the river like you did when you swam across the first time, only this time don't go across. Go down to the part of the river where you see pieces of a statue blown off. There will be a sandy part on the shore where you can get out. Walk around that area until you find the last golem in a kinda corner and you can get the last god orb from it
God orbs make the Iris weapons, which are the second strongest in the game (the strongest are the crystal weapons which can be found in the holy beast area outside of junk city; you can also find omega golem, one of the strongest golems you can obtain).
Almost Infinite SP / Parameters
If you go to the London casino and bet like other tips suggest (big bets and save and load technique) you can transfer the chips into TB by buying the endless supply of ''recovery powder'' and ''god's ambrosia'' and selling them at the nearby shop. You can only hold 9 of each at a time so you have to run back and forth to (each time you will get roughly 27,000 TB). Then you visit shops that offer ''skill gems''. Buy the ''skill gems'', go to the menu and go to the ''use item'' menu (to convert them into ''sp'' points) and apply them to the desired characters in your party (again you will only have the chance to hold 9 at a time).
The conversion of casino chips to TB (through buying and selling the two infinite items is somewhere around 16TB/casino chip.
An alternative to the roulette version of this trick is to play the slots. Play the higher stakes slots (ones where you have to bet 100-300 chips) and just keep pressing the action button to start and stop the slots. The TB Hunter DX machine seems to work quite well for this. I went from 5000 chips to 250,000+ in under 6 minutes. Tried the roulette way and had no luck..