The points from your Am ex gold are transferable, but hard to get good value out of those. If you have the Sapphire Preferred , the points are transferrable, and transferring to Hyatt could offer a good value. If you have the plain Sapphire, the points are not transferable. Citi thank you points are not transferable.

As for new cards, SPG is probably the most recomended card around here, but that's mainly behind the value of each SPG point. Depending on how you plan on using the points, they can stretch out quite a bit (cash and points). Priority Club card is also good for stretching out the points (mainly by point breaks, but also c+p).

If you're looking for straightforward free nights, the Hyatt or Fairmont cards are best. I'm not too familiar with the Hilton or Marriott programs.