I've been making a Ninja guide over what I've learned, and use for the last few years of playing NIN. I currently have a breif overview with some gear choices for 70+. I also include my reasoning for these choices and why are they are there, not just that you should use this blah blah.
Basically I've over my time done countless amounts of testing and this is what results show. It's still a workin progress as I update it when I have free time here at work. I will be making it slightly fancier over time as well as update situational things, such as Kiting sections and how to kite certain mobs. How to tank specific things. Gear optimization for lower levels in time. Certain BC's and what a NIN can do, Dynamis, Limbus. I have written a guide to Apollyon solo for NIN alreaedy for here a long time ago, I'll basically revise that as well as go into normal Limbus and what a NIN can do (when you're doing it with a group. I'd like to make it a very massive useful detailed guide.
I do not go into how to keep your blinks up, you should already know most of the basics of NIN, and how to obtain the spells and junk, it's not a solid beginner guide.
NIN Guide by Me You're welcome to post what you think here, or add comments or personal experience. If what I think you have to say is new, I will post it on my site giving you credit for it. If you have questions you me ask me.
I also have a message boad up there, TeamAwesome is my static xp linkshell where I level my characters along with friends I have a message board set up that I'll allow access to for this if you want to leave questions or comments there as well.
Later.