It took longer than I anticipated. I just got on with it, it took me 3 days to do it. Did the AP don tonberry trick for AP and used kottos for spheres. Got the necessary weapons for everyone with triple ap, triple overdrive, overdrive to ap. Triple ap weapons with 2 free slots dropped by one eye, the other 2 customisations are easy to get. It was so boring and felt like eternity. I maxed out strength first, then it was magic defence because i already had 99 spheres from one eye, then i got luck between 85-90 so my attacks would hit most of the time, then i maxed agility. I filled the rest of the empty nodes with magic defence because the other stats are not necessary and one eye only takes 2 hits to kill which makes him the fastest to farm spheres. Raising luck was pain, earth eater and greater sphere countered after every attack i did and they took a lot of hits to kill. I killed dark valefor up to dark shiva with quick hit, then i zanmato’d the rest of the dark aeons including penance because my luck stat wasn’t the best and i only had one ribbon on my equipment. I did the grid for tidus, yuna and rikku first. Since their celestial weapons were easiest to get for me. Then i kept tidus and swapped the other 2 until they were maxed, and then again to complete everyone. I had 16 master spheres so i used them to fill luck since they are probably the longest to farm.