I played Final Fantasy X-2 once, shortly after it came out back in 2003. (Or at least, shortly after I got it in 2003!) I played it a whole lot at the time, and I remember some things about the game but not all that much. I know it has a job system so right away it's awesome. It lets you tag in jobs on the fly sort of like how you tag in different characters in FFX. It went back to the ATB system but it was a little weird in that I remember being able to use a megaphoenix and then having my party get killed off but the megaphoenix would still resolve and bring everyone back to life. The game has a ton of sidequests and one short plot but you can play through the game multiple times while keeping a lot (all?) of your stuff between plays.
I also remember it has a completion percentage tracker and that something cool supposedly happens in the ending if you get up to 100%. I'm pretty sure I only got into the high 90s because I was trying to do it all without looking at the internet and I'm sure I was just missing something obscure. I eventually got bored or distracted or something and never did get around to finishing it off.
So what should my plan be this time? I definitely think my ultimate goal is to hit that 100% mark, but I don't think I need to ignore the internet to get there this time. I do want to see what I can do on my own though... So I think I'll probably end up playing through several times. The first time will be 'blind' and then after that I'll see how I feel about using the internet to find stuff I've missed.
I am also curious about what may have been added in the HD version. I started up a game yesterday and right away I got into a tutorial about a monster catching system that seemed completely new to me. I don't remember being able to use anyone other than Yuna, Rikku, or Paine in my party when I played last decade but I've already recruited Brother into my party as an uncontrollable monster. So either my memory is bad or I completely ignored this aspect or they added it in for the HD version. I'm expecting it's the latter, but I'm going to playthrough the game once before I go check.