Cheat:
How to win at Chocobo racing...
During a race hold down [Page Down] + [Target] to restore energy (takes a while).
After your party parachutes back into Midgar, you can get the W-Item Materia. Enter the subway tunnels in Sector 8. You can encounter the Turks, away from the screen, or go to another subway section towards the screen. Go towards the screen and the new subway tunnel. Follow the subway tunnel until it ends at a dead end; here you will find the W-Item materia.
Now, equip the materia on a character who has an item you want duplicated. When a battle begins, select the W-Item entry on the battle menu and pick the item