Pause the game, then hold R and press Down, Up, Square, Triangle, Triangle, Circle, Down, Up, Square, Triangle. A "Cheats" option will now appear towards the bottom of the menu, with "Invulnerability" and "Have All Weapons" options.
Pause the game, then hold L + R and press X(2), Circle, Square, Triangle, X. A "Artifacts And Keys" option will now appear on the menu.
Get a Gold medal in all eight mini-game challenges. Then, go to a shop Gargoyle and exchange the eight tokens for the Woden's Brand, which is the most powerful sword in the game.
Return to the Dan's Crypt level and complete it. It should be easy after you have progressed through other levels. Once done, you can get full health by collecting it, as well as a lot of gold.
After saving the farmers in the Haunted Ruins level, follow them to get a large stash of gold. Walk back to the bridge, save the game, and reload it to have the gold reappear. Repeat this as much as desired. It takes only a few minutes to get over 2,500 gold.