If you want a very populated server Asura is your best bet. Before you go, keep in mind, sometimes there are wait times for stuff. Most notable are ambuscade, salvage, einherjar, HTMB's (mostly selbina). Sometimes these waits are several minutes to near 30 minutes. Please don't be upset when it takes 3-5 mins for some of these events. Also, there are mercs for everything, participate if you want, but be ready to use your whole /blist to block mercs if you want to read shouts. I hear Bahamut is also pretty well populated with NA/EU. Although Odin has the second highest population, i believe its mostly JP. I spent a lot of time on some lower population servers to get a feel of that life. If you join a linkshell that does events and you make good connections, even those low population servers you can have a lot of fun. I personally enjoy Asura the most, but thats where most of my friends are, but sometimes those waits can really kill an evening. If your worried about paying the transfer fee, wait until its on discount, iirc around june/july its $5 to transfer. Another thing you can do if you want, create a mule on one of the servers (asura) and try leveling it up to 99 and joining a linkshell and give it a fair shot. Worst case, you cancel it in a few months, or if you finish RoV you can use it for DM augments lol. Hope you find what your looking for and if you do come to Asura feel free to reach out (I wont ignore you, but I do afk a lot)