In the Battle Arena of the Gold Saucer there are many good's that can be gained through hard work, determination and skill. Heres a list of all the stuff you can get from the Battle Arena:

Omni-Slash being Clouds Level 4 Limit Break, and W-Summon is a command materia which enables you to cast the same summon spell a multitude of times. You need this if you want to beat any of the Weapons.

Before you go into the Battle arena make sure that your HP and level is as high as possible, you've got double cut equipped (preferably with Clouds Ultima Weapon which you get after defeating Ultimate Weapon over Cosmo Canyon). Or, instead of 2x slash use Slash all which is probably the better option as you can kill the low HP enemies quicker. You also need lots of HP plus' (buy them from Cosmo Canyon materia shop), Restore, and a decent accessory such as a Escort Guard or Minerva Band. Some Summons might be useful although not completely necessary. Good Luck...

Some people have asked me where they exchange their Battle points. Well to do this you need to go near the entrance to the battle square area, to a big machine, not to the lady at the desk as most people thought. Press X near the machine and it will give you a prize for your efforts. Another bit of advice is not to leave the battle square area or the game forgets the Battle points you have, which is really annoying if you have a lot. If you get a tissue, it is not anything useful, just a item to add to the real life feel of the game. For novelty value really.

You can also get decent stuff from winning GP, the Gold saucers currency, like Gil. Get the EXP materia and increase how many EXP points you get after a battle! The best way to get GP is to win the Chocobo Races with a Chocobo you've raised. Look out for a Enemy Away Materia as a prize in the races, you can take the GP of 300 or the materia, but your probably best to take the GP to get the Gil plus materia from the lady at the Wonder Square.