I have to agree with Lem on all of this, the leveling comes naturally enough, you can "power level" by running FATES repeatedly. But the story quests keep you busy enough if you are targeting a single class. I'm not sure what to tell you about leveling speed, I'm in the middle of level 24 Gladiator now, this is with my character from beta phase 4 and early access, I have done minimal leveling of Archer and Conjurer, and Fisher and joined the Lancer guild, nothing else. Granted I don't play as much as many others can because of time constraints, but I am finding that with a 'normal' playing schedule, the game is neither excessively easy nor excessively quick to level. I like that very much, although falling behind everyone else so quickly is a little frustrating to me, but that's only natural given the differences in available playing time.
So my current levels are;
The gear situation for me is that for weapons and battle gear, the loot I am finding is better than anything I can buy, I don't know about crafting as I am not sufficient level in anything to do anything useful, and haven't delved into the HS crafted gear or the impact of melded gear yet. The developers say that HQ crafted gear with materia should be the best available at any given level, but I have yet to see. Certainly ordinary quality gear without materia is not as good as any of the loot gear at the same level.
Realistically I think it will be 2-3 weeks more before I get close to Gladiator lvl 50, and I have no idea how long it will take on the other classes. There is a mechanism called armory bonus which boosts the XP gained for other classes when leveling them if you have a higher level in your 'primary' class. I'm not sure how much that boost is though. If it takes me the better part of a month to cap Gladiator at 50, I can see that it will be a long, long time before I cap all the classes/jobs and crafting/gathering classes as well.
Not sure if that answers your question, I guess from my point of view, this game is not an easy speed run affair like some feared it would be. Like Lem says, Alkor has already reached quite high levels, though he probably has more time than most of us, and is quite probably better focused than most of us on the task of leveling. That's a good thing though, someone has to be first, and his experience will guide the rest of us.