You joined in a good moment to the game ^^.

Regardless of the servers, right now a lot of Free Companies are starting and recruiting members because with the PS4 the game is gaining a lot of new players.

Without exaggerating, every minute a new player enters the game. I tested in Limsa Lominsa Aetheryte plaza, awaiting for new people that came every two minutes or less and linked the aetheryte. And that was only one of the three starter cities of one server...Free Companies know that and now are recruiting like beasts. (Until the point I would call it spam...)

It depends of the tastes, but you should search for a small company, it is always better start together the things. You can check the profiles of the company before accepting an invitation ^^. There are also companies language-country based. For example I'm in one Spanish FC, since the game is not translated to us we are not many players, but it's a good environment. French and German FCs are bigger but probably a good option if you are from those countries.

If your native language is English then it depends of what are you searching more, big guild with a lot of advantages and people, or something smaller, not so many advantages but you'll probably know more the people and chat with them.