You'll feel like you've hit the jackpot if you collect 777 gold while defeating enemies. When you reach that lucky number, the game will award you with an extra 7000 gold for your trouble.
Lifedrop Glitch
From where you appear when you start the game, enter the first house you see and descend the rope. Enter the door and talk to the woman on the right, who will provide a chest that contains 5 lifedrops. Instead of opening the chest, though, keep talking to the woman. As long as you don't open the chest, the woman will continue dropping chests and you can collect a total of up to 100 lifedrops.
Sound Test
You can access a hidden menu that lets you play the game's various sounds by entering the following code at the title screen while New Game is selected: UP, DOWN, UP, DOWN, LEFT, LEFT, RIGHT, RIGHT.