Question

How do you find a golden magikarp?

Answer 1

If you are looking for a golden Magikarp, you are looking for a Shiny Magikarp. Shiny Magikarp are the only golden Magikarp in the game, so I'll assume that's what you mean.

If you are playing any game before X and Y, every Pokemon you encounter (besides a few with a "Shiny lock") have a 1/8192 chance of being Shiny. So your chances of finding that Magikarp aren't so great! Luckily, with techniques such as the Masuda breeding method, you can increase your chances to a more reasonable amount.

However, if you are playing X and Y (as your tags suggest), your chances doubled to 1/4096. You can also use fishing chains and the re-introduced PokeRadar to help find Shiny Pokemon. Your chances are still not very good though, so don't expect to find it very quickly.

Also, another thing I thought I should mention, those gold Shiny Magikarp don't evolve into gold Gyarados, if that's what you're looking for. It'll be red, since Shiny Gyarados is red.

Answer 2

You must rely on luck or try fishing. Chaining shinies to be exact.

Answer 3

You must be talking about a shiny Magikarp.

Finding a shiny is the odds of 1/8192, or 1/4096 in X and Y.

In X and Y, you can use the consecutive fishing method and get a shiny Magikarp very fast.