Very addictive and very rewarding game if you make it to the top. Patience required.
At the start, the game can be pretty difficult : you are left in the middle of town on your own and have to learn how to fight, how to do quests, and how to use the auction house. Although, most players are now veterans, so asking questions around help you through that phase.
At the character creation, you have to choose your race, appearence, and job. Of course, you can only pick between Warrior, Monk, White Mage, Black Mage, Red Mage, and Thief. The advance jobs ( Paladin, Dragoon, Samurai, Ninja, etc... ) will only be available to you once you hit level 30. You also have to quest them around.
Level 1 to 20 is difficult, especially when you do not have a subjob. Subjob can only be unlock at level 18, once again, after being quested. Afterwards, you can become, for example, a Warrior with Monk abilities.
In this game, you have to play with other people in order to advance. Soloing is only available for certain jobs, like Black Mage and Beastmaster, since they can handle themselves without support. In order to level, you need a balanced group, a tank ( tanks take all the damage ), Damage dealers, a Healer, and support ( example : Paladin ( Tank ), Damage Dealer ( Dark Knight, Monk, Dragoon, Samurai, etc.. ), healer ( White mage, Scholar, Red mage, Summoner ), Support ( Bard, Dancer, etc.. ). If the group is unbalanced, killing monsters will be a bit more difficult and slower.
Questing and doing missions can be very interesting. Square Enix tries to put a lot of comedy into their story lines, as well as meaninful plots. You really do feel like you are doing your part in Vanadiel through those quests, and they try to involve your character as much as possible in the cutscenes and such. Although, in the first expansions ( rise of Zilart ) your character is mostly standing there, but in the next ones ( Chains of Promathia and Wings of the Goddess ), they put a bit more emotions and reactions in your character to make you feel part of the story.
Unlike other games, you can change your job at will on your character, which means you don't need to do all the quests all over again to level a second job. Many piece of equipment also can be shared between different jobs ( like Ninjas can wear the same things as a samurai and a monk ). So equipement can enhance more than one job you have.
In order to get to the most interresting things in the game, you have to get to level 75, to the top. Therefore you will have access to many different events, such as Dynamis, Limbus, Salvage, Assaults, and fighting gods on a floating island. Those events give you special equipments, but they are very time consuming. You need to dedicate about 4 hours for Dynamis ( most groups goes twice per week, so it takes an entire evening ), While Limbus takes only an hour of your time ( yet again, twice per week ). Those events requires about 20-30 peoples in order to win. You also can fight stronger monsters, such as Wyrms and Behemoths with that amount of people. Although be ready to compete against rival groups for the same targets.
The crafting system is very interresting, but also very expensive. Although, if you can take up a craft that high and make rare things, the money you spent level it will be refunded eventually.
To resume, you have to dedicate a lot of time in order to really enjoy this game. Talk to people, make contacts, make friends. Thats how you will make it to the top. The key to this game is socialization. You *HAVE* to talk to others. The road to the top is long, but once you get to level 75 it will be very rewarding. Give the game a chance and be patient.