I think your choice of the Amex Gold card is a mistake for actually using it for purchases, though I assume you got a nice bonus for first use and got it without annual fee for a year. For actual use, the Starwood Amex card gives 25,000 miles/$20,000 spent on most airlines except United and Continental.

Once you have decided on you airline program(s), look at my website below for free mega bonuses. The best are on the Credit Card and Finance pages. You can get huge bonuses from American Airlines, for example, by getting its personal and business Mastercard, its personal Visa card, and its Amex card. That's an easy free trip to Europe - well, free except for the fees added for the ticket.