I am not 100% sure on this but, (I think) minecraft on market place is ONLY available to gold customers (to download that is) ..
Like trigger said, you usually get a month for free anyway as a taster.
That said some high street stores, and some cleverly renamed by me online stores (to avoid being accused of advertising) amazong, and gameR , have minecraft to buy over the counter (so to speak) . It comes as a gift card, you still require net connection though, and sadly I do not know if you still require gold to redeem.
Best thing however, is to not get the game, as your life will be forever ruined by trying to make Optimus prime out of wool.