Coeurl actually has plenty of friendly players, it's just that unfortunately spam messages from gil-sellers have turned most players off of using the global channels much. Most chat has moved to private Free Company, Linkshell, or Party channels. Your best bet for a more social game experience there is to find a good FC or a few linkshells to join. And in the main cities or wherever there are plenty of people, you can often get conversation going in /shout or /yell if you kickstart the conversation with a question or observation on the game. It's just that your chances of coming across such conversations already going on are slim.

As for Sastasha, it sounds like you're ready. You'll actually get three dungeons practically in a row at this point in the storyline, Sastasha, Tam-Tara Deepcroft, and Copperbell Mines, before the story returns to another sequence of solo quests. But these first few dungeons are pretty straightforward, designed for new players who are still getting comfortable with their class, their role, and often MMOs in general. The only thing that might be an issue is that you may get a party that wants to race through them as fast as they can run without giving you the time to really see what's going on the way most new players would prefer.

Look me up in the game (character name Y'kayah Tia) and maybe we can do some of them together. I'm on most evenings (Eastern time zone). Or I craft, too. I could make you some good crafted gear that's better than quest rewards (though not as good as some of the stuff that can drop from those dungeons' chests if you're lucky).