Begin to enjoy playing FFX and its battles, because if you are not going to use Zanmato (five times in a row), your stats need to be huge, and levels are the way to salvation. Essentially, having 255 stats in everything except Luck (unless it is easier to obtain Fortune Spheres in International, then go ahead for them), will help. To get 255, get the Purple Spheres that increase your stats, and fill up the empty nodes. If you want, get Break HP Limit for at least 3 characters, complete the grid with at least 3 characters, and get at least 3 of the Celestial Weapons (or customize for Break Damage Limit).

Break HP Limit: 30 Wings of Discovery
Kill Shinryu for 1, or 2 if Overkilled
Bribe Marlboro for 675(?)k gil to get 3, 4, or 5 Wings
Bribe Greater Marlboros (I don't know the amount), anywhere from 6-10

Break Damage Limit: 60 Dark Matters
Kill Arena Monsters (Area, Species, or Original). Randomly drops one DM, or 2 if Overkill. The easiest one to kill is Stratotavis, whose HP is less than four 99999 damage hits, and his attack stats are the smallest. (Area Creation)

Purple Spheres (unless they changed the monsters who drop it in International, these should be more or less, accurate; all of these are the Species Creations; drop patterns apply: 1 sphere is dropped, or 2 if overkill)
HP: Ironclad
MP (useless, you can max out 999 with the ones on the grid): Vidatu
Agility: Fenrir; Evasion: Pyterx; Accuracy: Hornet
Strength: Juggernaut; Defense: Tanket
Magic: Jumbo flan; MDef: One-Eye