Here's the problem.... your probably not going to find people that are "legitmately building experience points party's" level's 30-75. It just isn't how things go now. Basically follow yygdrasil's guide so you understand what's happening, and after you've solo leveled your job to 12ish-15ish, join a Gusgen mines party. They spam GoV pages and level sync so a full alliance get's fast exp. It's sort of like a mini-abyssea.
After 30 you can start your searching for experience points parties, but i'm gonna be honest, it's going to take you a long time to level a single job to 75.
Find a friend, or someone who doesn't mind letting you leach. You'll be invited to a exp party in one of the zones. You stand around not doing anything until your lights are built up and you start gaining exp. Often times when this occurs, the level 30 job will be the "curor guy" and he'll run around with 2-3 stacks of keys and open up the chests that drop from the mobs, since he can't do anything else.
The thing that's going to cause that not to work for you, is the fact that you don't have the level cap quests complete so your going to have to leave abyssea, reseting your lights, and then go do the quests. You'll probably need some high level friends to duo them with you.
Thing is, Jarre said it best. Learning your job.
Here's the thing about the FFXI community, and hell, most MMO communites. .3% difference to hardcore gamers means the fucking world to them. If a war does a weapon skill on avg. for 1000dmg and a dragoon does a weapon skill for 970dmg, guess what job people are gonna want you on. It's a stupid attitude with most hardcore MMO players, and it's pretty pathetic. There aren't many games that can balance the different class/jobs/professions well enough that taking any sort of job combo will work, in these hardcore players eyes.
I considered myself pretty hardcore when I played, but this attitude was one of the reasons i quit. It's pathetic when players figure out a way to win a fight, and then immedietly get the idea that "THERE IS NO OTHER WAY TO WIN UNLESS YOU BRING THESE JOBS, WITH THESE ABILITIES, BLAHBLAHBLAH". I'll admit i'm still wishy washy on this also. It's that way in XIV, but definetly not to the extent it has gotten to in XI.
Where was I going with all this? Well Jarre was right about learning your job as you level, however, I don't think leveling 1-75 is going to teach you anything about fighting NM's at level 99. Honestly the only thing that leveling is going to give you is muscle memory for the way you've setup your skills in your macro bars. I feel this is the problem with all MMO's. Learning your Ability rotation is pretty simple once you have all your abilites, and if you get your job burned to level 99, and then learn your abilites, I see no harm in that. Especially in a Square Enix MMO.
Good players are going to be able to jump into a level 99 job they've never played before and in 1-2 days are going to understand how to gear it for certain situations, macro for certain abilites/weapon skills, and they'll research mobs that they've never fought before, before they fight them.
I have never played scholar, however, when i was playing i abyssea burned my mule to level 95 scholar. I had mediocre gear, but i made sure i got all my spells off the AH, and I actually swapped gear for whatever spell/ability/situation i found myself in. Was my gear top of the line? no, but again, abyssea made alot of folks realize that .3% isn't going to ruin a fight. But not casting cure, or haste, or stoneskin, or using your 2hr when your supposed to is.
Sure you have hardcore players that say things like "oh i can trio anything in abyssea with a Mnk/whm/Blm, and hell you can. But that doesn't mean you can't also bring 8 people to that same mob. It doesn't mean that the other 17ish other jobs are useless, its just them trying to flex their e-penis, as if soloing carabosse on your ninja will go onto a job resume later in life. Anyway. I digress....
Anyway, went off on a bit of rant there, but seriously, your probably gonna have a hard time finding actuall eXP parties like were abundant back in the day.