i would probably say there was somewhere between 500 and a 750 spheres on the starter grid and a good 900 on the elite grid. just an estimate though. took me a good 100 hours to get them all maxed out wtih clear nodes and various tasks. though its not really worth attempting if you dont have the legendary weapons.
theres 7 main characters: tidus. wakka, lulu, kimahri, auron, rikku, and of course yuna
and one other playable character: