From what I hear, Ragnarok is a good server if you're looking for raid progression. Otherwise, you can't go wrong with Phoenix, Odin, and Cerberus (I recommend Phoenix as it is a big server with plenty of activity going on). I wouldn't recommend Moogle due to the majority of the French playerbase being bad at the game, and I've seen people transfer to Phoenix from other servers and are enjoying their stay here. If you ask me: Ragnarok, Phoenix, Odin, and Cerberus are four of your best options.