What is a good active server on the US that is a good place to start?
You'll often see Balmung and/or Gilgamesh as the answer to this question, but getting a character created on either server can prove to be a nightmare...especially for Balmung. SE locks servers for new character creation once they reach a threshold of people online on the server, and the two servers I mentioned are by far the most populated in the game.
One area where lower population servers have a major advantage: Housing. There are servers who still had housing plots available even before last patch added more housing wards to every server. Meanwhile, those new housing plots were all sold 20 minutes after Balmung was available to log in on patch day.
It might be a little late but I recommend Faerie as a good server to be on. Still plenty of people around and some very nice and helpful FC.