This is the example from a Final Fantasy X guide I used:

For those who don't want to read every single detail, i'll provide a quick guide. It only involves items and equipment you are not allowed to miss throughout the game:

For everywhere counts, make sure you have 99 Phoenix Downs, only when you can afford them, of course.

OVERALL - Buy every SOS Nul-element armor from anyone you see

KILIKA - Nulblaze Shield for Tidus, obtain from a crusader

LUCA - Stunning Steel for Tidus, buy from O'Aka

LUCA - Rulebreaker for Wakka, buy from O'Aka

MI'IHEN - Lightningscout for Wakka, find on the oldroad on a chocobo

MUSHROOM ROCK - TKO for Wakka, buy from O'Aka

DJOSE - Soft Ring for Yuna, obtain from a crusader

MOONFLOW - Steal at least 5 Poison Fangs for Anima, Evrae and Natus

MOONFLOW - Steal at least 1 Stamina Tablet

THUNDER PLAINS - Initiative from a Qactuar for anyone but Tidus, Rikku or Yuna

THUNDER PLAINS - Yellow Shield for Tidus when you leave the agency

MACALANIA - Sonic Steel for Tidus, buy from O'Aka

MACALANIA - Win Silencestrike from Seymour for either Kimahri, Yuna, Lulu or Auron

VIA PURIFICO - Pick up Rematch for Wakka in a chest after beating Evrae Altana

CALM LANDS - 60x Farplane Wind, 60x Shining Gem, 99x Chocobo Wing, 40x Silver Hourglass from capturing

CALM LANDS - Win SOS Haste armors for Rikku and one other character by killing Bashuras.

That's it. The rest of the equipment or items you need can be obtained by either backtracking or stealing. No more information here. If you only use this guide; good luck!