I was on the Island closest to Hell, drawing good magic from the drawpoints to help with Omega. I got all the non drawable Gf's, Bahamut being my best one. Tonberry's abilities for shops became very useful.
After I had loaded my party with healing items etc. I decided to go on with the story. *Sigh* Seifer was actually really easy, 'cause Rinoa's Angel Wing LB along with the really good magics I got from the Island Closest to hell wiped him out.
Adel was really tough, sonsidering I didn't have Rinoa... but I managed to get passed her. As for Ultimecia, I'm still trying, although she's remarkably tough, and it's really frustrating.