This method is only possible if you run the game on an emulator. And you need a "Hex-Editor". First step: Save the game by walking into an inn. The emulator generates a new save-file [filename.sav] on your harddisk. Open the file in the Hex-Editor. The graphic shows were to find the values for "Gold" (green rectangle) and "Experience Points" (red rectangle) for the first character in your party.
The first character has 9000 Gold (hex: 2328, but in this case you have to turn it around!!, so it is 2823) and 5064 EXP (hex 13C8, and turning around again makes C813).
Walk into an inn and save the game. Restart the game and create a new character. Put him into your party and transfer all his Gold to one of your regular characters. Save the game. Restart again and erase the new character and create a new one (to get more gold) or put your old character back into the party (to continue with the game). You can do this procedure as often as you want.
Use a Moongate to teleport near Castle Exodus. Normally you can't enter the castle because of the water. But if you are incredibly lucky there might be a pirate ship. Fight the pirates and get the ship. Now you can enter the castle with the help of the ship. But remember that the enemies in the castle are very strong. So the best tactic is to go back to an Inn and safe the game first before you enter the castle.
I discovered this on accident, but you need to erase a save game slot, or preferably one that was never used. Create a ready made party and then shut off the power to the nes. Restart it and create one to three new characters. Without forming a party select continue, you will have your regular party plus a ghost character (random sprite) who has all the weapons, armor, and tools in unlimited quantities and a dummied out weapon called the fightr'saxe (it's much stronger than the mystic weapon). If you take gold from the ghost, a katakana symbol will appear by the gold amount, and you can take an unbelievable amount of money from them. The only down side is that the strongest monsters in the game appear right off the bat. What I did was get the best stuff from the ghost and a whole bunch of powders, then fought balrons and kept freezing them. Then I went to ambrosia and maxed out everyones stats then dumped the ghost. I was able to beat the game in about an hour using this method.
You get to make many guys, but only four of them are played at once. So you got your main party, and one of your guys ends up dead, but you made too much progress to reset, or maybe one of your guys got turned to ash! Don't despair! Make four new guys. Then go kill 'em. Don't feel bad, their sacrifice was to a worthy cause. Now if you notice, the first guy in line got resurrected automatically and whisked back to the castle. How convenient! Go save it. Reset, and form a party with the guy you really want to resurrect up front and the other three dead guys backing him up.