Arcell is pretty much spot-on with all of your points. Of course, I'd recommend you come play on Lindblum, as we are fairly populated (not as much as Mysidia, Cornelia and possibly Besaid, but pretty far up there) and have an active community, but I'm biased, haha. As was also mentioned, Ul'dah is the most populated, but you shouldn't let that influence your starting nation. A walk to Ul'dah from Limsa Lominsa and Gridania is only like 30 mins. and it's a mostly safe path.

If you are going to wait, I wouldn't wait for long with Patch 1.18 coming out mid-June. In my opinion, you might as well start now and get a hang of the game so you can be prepared for the dungeon that will be released as part of the patch. While there hasn't been anything substantial added content-wise, the game does have a much better feel to it since release.

As Black_Rose mentioned, the game is still free-to-play, so since you already bought the game, you don't really have anything to lose.