This post has general overview of all jobs if you're not sure on what to choose:
https://www.reddit.com/r/ffxiv/comments/3lzt4r/are_you_new_to_ffxiv_cant_decide_what_class_to/
Some more that I can think of:
1. Your starting race and clan have different stats allocation, but it's very very very minor, barely has any effect in the long run. So don't choose a race based on your class, pick the one you like most.
2. Alt character is not needed in this game. You can change to any class anytime after you reach level 10. So don't think too hard on your starting class, you can become any class with one character.
3. DO NOT SKIP CUTSCENES. Even though it's an MMO, it's still a Final Fantasy game. so expect a great story with some great cutscenes. FFXIV story is one of my favorite in the series other than FFVI and FFVII.
4. There are three types of quests:
Main Scenario Quest, doing this is your main priority. Around 80% content in this game is story locked.
Side Quest with this icon unlocks content like dungeons, classes, locations, and even features/game mechanics. So be sure to complete them.
Regular Side Quest. These quests only gave you experience and sometimes items/gears. Completely optional. Do not pick up every single side quest. You will need them to level up your other classes. Especially at lower levels, most of your exp is going to come from story quests. Between those, you can do your hunting log, levequests, fates, and maybe a few side quests.
5. At lower level, the combat might seem slow and sluggish. This is the most common complain for FFXIV. It will get much better when you reach higher level since your GCD (Global Cool Down) will get shorter and you'll have many more skills and mechanics.
6. If you haven't bought Heavensward. You don't need to buy it immediately because all Heavensward content is locked if you haven't finished ARR main story. So you can buy it later when you finally finish the ARR story. There's some benefit that you can get by having Heavensward early though:
a. You can select Au-Ra as your starting race.
b. You can descend deeper than floor 40 (or is it 50?) in Palace of the Dead (roguelike dungeon).