EE28-EDAF Start new game with 255 GP
6D28-EFDF Start new game with 32,768 GP
EE28-EFDF Start new game with 65,280 GP
6F09-8707 Start new game at Level 16
EE6B-8738 Chest in elder's basement in Potos gives you 65360 GP
C274-8764 + C277-8DA4 Staying at the inn in Potos is free if you have 
enough money
CE5F-5767 Items in the shop at Potos are free if you have enough money
DDEB-E544 Candy costs nothing
DDE3-E044 Overalls costs nothing
DDE8-E9C4 Bandanna costs nothing
DDEC-E9C4 Cup of wishes costs nothing
DDEC-E944 Medical herb costs nothing
DDE7-7047 Wristband costs nothing
DDE8-E144 Hair ribbon costs nothing
DDE8-E1C4 Rabite cap costs nothing
DDEC-E0C4 + DDEC-E034 Faerie walnut costs nothing
DDEC-E044 Royal jam costs nothing
DDEB-E5C4 Chocolate costs nothing
DDAB-E715 Staying at Neko's(tm) costs nothing instead of 30
8208-776D Protection from most hits--Switch off to kill enemies

For the rest of the codes you can't save the higher level attributes
9C06-81AD Strength for level 16 is 90
9C06-85DD Agility for level 16 is 90
9C06-850D Constitution for level 16 is 90
9C06-856D Intelligence for level 16 is 90
9C06-85AD Wisdom for level 16 is 90