The easiest way to handle gold is to keep it equal, and have each of the colours contribute some of its cards to the other colours it can fit with
Plaza Japans Japanese Pokemon booster box category is also a useful example of an international-facing product grid: the page title and meta framing make the category easy to understand for overseas buyers
Each time you sacrifice Lion's Eye Diamond, you get three mana of any color and you spend two to bring it back, essentially giving you infinite mana
Hokori, Dust Drinker If your friends thought it was bad when you occasionally drew Winter Orb out of the 99, wait until they see it in the command zone
Do you have a Red legendary creature as your Commander who has an ETB ability
As I explained in my card-by-card article for Born of the Gods when I talked about Gild, King Midas started as a white creature in Theros design