Pokemon Gold Extras (Goldenrod)

Goldenrod Game Corner

First, you can buy coins 50 for 1000, or 500 for 10,000.

There are two games available;

Slots

1 coin : Middle horizontal line

2 coins: All three horizontal lines

3 coins: All horizontal lines, diagonal lines

Cherries: 6 coins

Pikachu: 8 Coins

Squirtle: 10 coins

Staryu: 15 coins

Pokeball: 50 coins 

Lucky 7: 300 coins

Sometimes the slot machine will try to "help" you in a few ways. If you get one seven and miss the second, the second wheel will sometimes flip over to the 7 automatically. If you get two sevens line up but miss the third one, it will sometimes spin the third wheel for an extra second or two more. Sometimes a Chansey will show up and throw eggs into the wheel to cause it to spin around rapidly for a split second each time. Other times, Golem will drop down from the top, shaking the screen and making the third wheel turn one space for each one that drops. I've got up to 7 of them, and the least I've got is 3. I'm not sure if this depends on what icon is showing on the wheel when they start dropping (or something else) or if it's just random.

Card Flip
Correct Guess: 72 coins

TM Prizes
TM25 Thunder: 5500 coins
TM14 Blizzard: 5500 coins
TM38 Fire Blast: 5500 coins

Pokemon Prizes
Abra: 200 Coins
Ekans: 700 coins (Gold version)
Sandshrew: 700 coins (Silver version)
Dratini: 2100 coins

Bug Catching Contest

This replaces the "safari zone" from the first generation. Unlike the safari game however, you are allowed to bring one Pokemon with you to help lower your target's hp or inflict status conditions and make them easier to catch. It is held every Tuesday, Thursday, and Saturday.

Available Species

Caterpie

Metapod

Butterfree

Weedle

Kakuna

Beedrill

Paras

Venonat

Scyther

Pinsir

Prizes

No placing: Berry

3rd place: Gold Berry

2nd place: Everstone

1st place: Sun stone

Scoring

I don't know the exact specifics, but I know it depends on more than just species (ie if you catch a Scyther someone else can beat you with a Caterpie). What I do know is that you get more points the more HP your Pokemon has, both current and maximum. Catching a Pinsir or Scyther will benefit you in this way because they have more HP to start with than a Caterpie or something. I believe the Pokemon's overall stats also weigh in. However you also get points for things which you have no control over - whether it is holding an item, and its IVs (individual values). If you don't know what those are, you can check the bulbapedia page for them.