Diamond is always the best since you get the most amount of rupees and you get more reses. Although, I always thought it should've been $15 since that's how much it usually would be worth. One day, I want to get diamond or gold. For you, I would rather choose gold than iron since iron is practically useless. All you get are 400 rupees and a few supporter abilities, and that's it. In gold, you can get another res and get more rupees. I would choose gold over iron.
lol, I am too. It uses your operating system, which is Mac. Anyways, I asked this awhile back, to get gold or Diamond. I got gold and I love it
Gold gives you a lot for your money. 2 res's, access to the Utopia wild and nether, access to Endertopia, the ability to hide from the map, and custom colored res messages. Where as diamond only gives you 2 more res's, the ability to fly in Utopia town, and the ability to use TnT.