Short answer: Not very.
Long answer: Basically, Abyssea has made the leveling process from 75-95 pretty straightforward, and you can enter it at level 30, but you'll typically have to pay for the privilege, or have friends take you in. Prior to that, in a similar fashion, Grounds of Valor (the dungeon equivalent of Fields of Valor) have made it pretty easy to get your jobs up. I've taken 3 jobs from 37 to 50 in one afternoon in the Crawler's Nest, for example. In the long run, skilling up will take more time than leveling.
If you've got friends who still play, it'd be fairly simple, all things considered. If you don't know anyone though, could be a little tricky to do things like subjob quests, since I doubt you'd be able to find too many people who needed lol.
And I'm pretty sure you can just pick a server these days. Dunno for sure tho', haven't actually made a new character since 2007.