There are a myriad of mini-games located in Wonder Square and nice collection of prizes that you can turn the GP won from those games in for.
Potion (1GP)Ether (20GP)X-Potion (80GP)Turbo Ether (100GP)Carob Nut (500GP)
Gil Plus Materia (1,000GP)Experience Plus Materia (2,000GP)The last three prizes start off listed as “????” when you view them until you purchase them using your GP. Spend the Gil you have on a Gold Ticket (which gives you free admission into Gold Saucer permanently once you buy it) rather than wasting GP on it as it’s far too expensive to spend GP on.
Gil Plus Materia and EXP Plus Materia are barely worth the effort needed to obtain them. Spending the time to level up your characters or level up Materia to sell for money is much less grueling than trying to earn that much GP and then having to go battle with the Materia equipped anyway.
All you have to do is tap the 
Button as rapidly as possible. You will obtain 1 GP if you beat the Sumo Wrestler and 2 GP if you beat the Wrestler. The game is 100 gil to play.
The Super Dunk mini-game requires quick hands and good timing and a measly 200 gil to play. The idea behind it is to hold down the Button for just the right amount of time which ends up being about 1 second. This occurs right as Cloud stops moving and right about when the ball touches his head.
Every basket you score nets you 1GP and after 10 shots you’re given the opportunity to double your points or lose them all (Double Chance). If you hit all the baskets successfully and double your GP each time you can walk away with up to 300GP!
The Wonder Catcher mini-game is a completely random mini-game that costs you 100g to play. The prizes you can potentially win are as follows:
Potion (39.1%)Ether / Phoenix Downs (2.0%) **Megalixir (0.8%)** The prize list is different depending on which side of the machine you play on. You can receive a Phoenix Down on one side and an Ether on the other, although it’s important to note that due to a game glitch the sides are actually switched.
The side that says you can win an Ether actually awards you with a Phoenix Down while the side that says you can win an Ether awards you with a Phoenix Down.
This game costs 200 gil to play and is an exact replica of the mini-game you had to play when you first had to escape from the Shinra Building. The only difference this time is that you don’t have to worry about keeping the health of the characters in the truck up because there’s no impending boss battle at the end of the road.
The orange bikers will go straight for the truck to try and take it down while the red bikers will drive away from the truck and stay on the outskirts. In order to ensure a maximum score you will have to take them all down and as quickly as possible to get more to spawn before the end of the track. You gain 500 points for each biker you take down and you lose 25 points each time the truck is hit.
You get 10 GP if you can get over 10,000 points (plus a Speed Source the first time you play). 2GP if you don’t.
Corel’s Angel
You will also receive the Corel’s Angel Trophy if you are able to obtain a score of 10,050 or higher during your game.
The Crystal Fortune “mini-game” is just a fortune telling machine that gives you a different fortune at various points in the game, often times related to the actual story and point in the game you’re at.
First visit: Use caution in relationships.
Leaving Corel Prison: Your lucky color is red. (The Buggy you escaped in)
Leaving Cosmo Canyon: You may meet someone new. (Vincent, an option secret character)
Leaving Nibelheim: You have ties with those that fly. (Cid joins your party)
Leaving Rocket Town with the Tiny Bronco: What you are looking for is near. (The Keystone is in Gold Saucer, Dio has it in Battle Square)
After getting the Keystone: Use caution in relationships. (Cait Sith steals the Keystone)
After the date scene: What you search for is in the Southeast. (The story continues at the Temple of the Ancients in the Southeast)
Leaving the Forgotten Capital: A great turning point is near.
After you get the Highwind: Never give up.
The Mog’s House mini-game is more of a story and a really boring one at that. Your only job during this story of a Mog finding its true love is to feed it some Kupo Nuts. The way of actually knowing when to stop feeding it is to listen to the sounds it makes as you feed it.
When he’s full he’ll make a different noise. But you’re here for answers, right? The first time you feed him give him 5 nuts and 3 nuts the second time.
The first time you play the game you’ll get 30GP from the man who stands over your shoulder watching. You’ll get no more prizes for playing this incredibly boring mini-game though, so don’t bother playing it again.
3-D Battler is a 200 gil mini-game that appears to have something to do with your button pressing skills, but is really just a random mini-game. It’s much like rock, paper, scissors, except that the battlers later on in the game have a really high advantage.
The first round is against a girl in pink. You have a 90% chance of beating her. The second fighter is a wrestler (70% chance). The third is a dude with an afro (15% chance) and the last beatable wrestler is a red spaceman (10%) chance.
The final battler is called the “Invisible One” and it’s impossible to defeat him. However, if you managed to make it this far you’ll be awarded 300GP which isn’t bad. The down side is the random aspect of making it this far. When all the chances to succeed and fail are added together you have an approximately 1% chance of making it past the red spaceman, so good luck! You’re going to need it…
This mini-game costs 200g to play and is a repeat of the snowboarding mini-game you play when you exit the Icicle Inn. It only becomes available after you’ve already passed the Icicle Inn part of the game when Gold Saucer is accessible in Disc 2. Press X to jump, square or down on the directional pad to brake and L1 or R1 to “edge”, which allows you to make much quicker turns.
You’ll be given the option between 3 possible courses: Beginner (A), Advanced (B) and Crazy (C) and you’ll win a prize if you score 90 points or more.
The prizes are as follows:
Safety Bit
All Materia
Crystal BangleYou can only win the Safety Bit, All Materia and Crystal Bangle one time.
Obtaining Points: You can obtain 40 points from balloons, 30 points for your time and 30 points for your technique. Red balloons are worth 1 point, blue balloons are worth 3 points and green balloons are worth 5 points. You’ll lose a point for every obstacle you hit. Lastly, you’ll lose a point for every 2 seconds longer you take on the course than the times listed below:
This mini-game is available after you’ve already completed the Submarine Chase mini-game to recover the Huge Materia near the Underwater Reactor. There are four level options available (1, 2, 3 and 4) and the prizes for successful completion are as follows:
InkT/S BombDragon FangDragon ScalesCauldronYou can repeat the mini-game to receive more GP, but each of the items (Ink, T/S Bomb, Dragon Fang, Dragon Scales and Cauldron) are only available the first time you complete the level.
Speed Square is a mini-game that is not found inside Wonder Square; it is its own location in Gold Saucer.
It’s a roller coaster that allows you to shoot at targets as you continue along the tracks. The only way to get good at it and start getting high scores is to play through it quite a few times and know where the targets are located. Aim for the red wheel of the boat. A direct hit can yield a massive amount of points. The prizes are as follows:
3000 to 4999 points:
Masamune Blade (50%)1/35 Soldier (25%)Super Sweeper (25%)5000+ points:
Both the Umbrella and Flayer can only be earned one time.
For more information on the Battle Square challenge check out the Battle Square side quest section of the walkthrough.
Check out the Chocobo Racing and Breeding side quest section for more information on how to win Chocobo races and win prizes.
Umbrella
Flayer