Check this out. This will teach you step-by-step how to make your own gold sprayer and also introduce you a little bit to the mechanics of modding your own stuff.
Also, the Cortex Command wiki will also provide you all kinds of great information that the tutorial I gave you might not explain. And remember: search function will be your best friend.
You could just add more gold to the map itself, but it ruins the legitimacy of it for those times when you might want to do an honest run, so I recommend that or adding gold to your funds via the developer's console over changing the vanilla content any day.