I buy it 10' at a time. You get enough to do 2 bikes and have some to spare or a perfect amount if 1 of them has a jackshaft. You also get 6 master links, so you'll have spares if you lose one. I guarantee this won't be your last mini... 1 is never enough and variety is the spice of life!
I don't believe there's any major difference between gold on black and gold on gold chains. And although I prefer to only run 1 master link per chain, I have pieced one or two chains together before with no issue.