I joined FFXI for the first time in June 2015 and I've adjusted very well (imo). First thing, as mentioned above, is use the wikis. Learn them. Love them. Bookmark them. Ffxiclopedia wikia is great for all pre-Adoulin missions and quests. Bgwiki is great for in-depth late to endgame content like Adoulin content, Abyssea, and all Rhapsodies of Vana'diel stuff. FFXI AH is great to learn more about your server's economy, other players and linkshell info (limited), and has some great guides for jobs. Unfortunately, some stuff is severely outdated so you might want to ask other players directly for later game stuff.

Second thing I'd suggest is joining a Linkshell immediately. Many beginner friendly Linkshells should have pearls available at the concierge NPC. Just grab one (or many) and see which Linkshell is a good fit for you. Other, more experienced players are invaluable. They can teach and explain things the wikis can't. They can help you through difficult fights or lend a hand farming something or leveling you up at higher levels. I wouldn't be where I am now without my LS mates.

I say if you're planning on putting in a lot of time into the game (level 99, Job points, legendary weapons), you'll want to do research into how your job works and that kind of stuff. If just going at your own pace and feeling the game out, you should be okay on your own/with your LS.

I solo'd basically from 1 to maybe 60+ before I found a LS. I still pretty much soloed except if someone allowed me to leech a few levels, but my LS introduced me to Dynamis, Abyssea, gave advice on what to do next (or first), and explained game mechanics I probably wouldn't have learned about unless I specifically sat down and research game mechanics on my own. I was stuck in Bastok until about level 30 and I didn't think anyone else played this game because there were few to no players in Bastok at that time. My mind was blown when I made it to Jeuno. Where were you guys this whole time?! The game isn't dead despite what the haters say. Maybe not what it used to be but lots of people still play this game and it's probably the easiest it's ever been to be a brand new player.