Begin with an Amex Card with lower requirements
My personal advice would be: Just apply for a Green or Blue American Express Card which has lower requirements concerning the minimum salary.
If itīs a green one (at least in Germany) it bears the same privileges in view of collecting the MR points. ^ And after some months of use your credit limit may increase and Amex *may* offer you an upselling to the Gold Card.
IMHO there is no reason to start with an Amex Gold Card.
So try this step-by-step approach. And with a longer relationship with Amex and several months or years of charged and paid balances your relationship will improve. At least in Germany it works that Amex offers you the credit cards of the higher tiers after several months/years of faultless history.
It would be sad if you would miss the opportunity of collecting MR points.
So start with the cheapest colour of Amex which delivers (to Airlines ) transferable MR points. As I donīt know which co-branded cards are out there in the US I just would start with a green one.
Hope this helps.