Come to Bismarck; I'd like to have more friends.

We're friendly and we won't bite.
There have been server merges over the past few years.
But a few changes off of the top of my head:
- You no longer lose EXP from levels 4~30. After 30 EXP will be reduced.
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Synergy. A new way to synthesize.
-- Synthesis no longer has a waiting period between each attempt! And guild stores no longer have a waiting period between purchases!
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Abyssea. This will be where you will gain most of your exp, armor, and gil. As soon as you hit level 30 you will want to talk to Joachim in Port Jeuno (near the stairs to the Auction House/Chocobos). He will give you a Traverser stone, which you will want to take to one of the 9 Maws for a cutscene. One of the easiest maws to get to (and one you will be using the most) is Abyssea - LaTheine's, which is found right at the entrance from West Ronfaure. Click on the maw, get a cutscene, go inside, talk to the Conflux Surveyor, accept visitant status (and use your stone), then leave and return to Joachim. With this all said and done, you will start accumulating Traverser Stones (one per 24 hours) which you will need later.
-- In conjunction with Abyssea, you will want to look into
Abyssites. The first Abyssite type you want to go after is the three Celerity; these will reduce the hour cooldown between stone accumulation while also multiplying the stock you currently have. The minimum period between stones is 8 hours.
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Fields of Valor and
Grounds of Valor for exp. Both are very handy.
- Level sync. It allows all members in a party to lock their level to another party member's. Only applies to a party, not the entire alliance (so each party in an alliance must have a syncer). Can only sync down, not sync up.
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Trials of Magians. Great way to build weapons and armor. At level 30 you can get job emotes with them. Level 75+ you can start building weapons and armor. Weapons vary from basic ToM weapons, elemental weapons, and empyrean weapons (which rival relic/mythic in power). The armor is the af3 set, which can be +1ed and +2ed from items obtained in Abyssea (your job's paper seals for +1, and specific gems for +2).
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Dynamis has been greatly changed. You now must purchase an Hourglass Key Item for 100k (and can buy maps from the same goblin) from the old goblins that gave the original hourglass. It's permanent and you can enter Dynamis once a day. Monsters are no longer true sound or sight and you may sneak past them. It's important to kill all of the Time Extensions, and you must proc certain monsters in certain ways (with magic, job abilities, or weapon skills depending on the type they are). Click the link to read more on it.
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Voidwatch is the new end game. Consider clearing it all even if it's not the most pleasant activity; clears give you accesses to beneficial teleports all across Vana'diel.
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Nyzul Isle Uncharted is Nyzul 2.0. I've yet to attempt it, I heard it's pretty vicious, but the armor rewards are worth it.
That's all I can think of for now.