Which is Better for White to Learn, KIA or King's Gambit?

@Battledressing if you play 1000 white games with 1.e4, you can expect about 3 games Latvian 1 e4 e5 2 Nf3 f5 and about 4 games Elephant gambit 1 e4 e5 2 Nf3 d5. It is a waste of time to prepare for that as it is so rare. It is also futile to prepare for 1 e4 Na6, 1 e4 Nh6, 1 e4 f6 and so on. If you face it you just think carefully about your moves, develop your pieces and play for the centre and you will be fine. After your game you can book up on it to see how you did if you like. If you prepare for these rare openings, you spend time uselessly and by the time you ever face it you probably have forgotten your analysis. It is different if you know that you play in a tournament against a player that regularly plays Latvian or Elephant Gambit. Then it makes sense to look into it beforehand.
On the other hand if you were to play Latvian or Elephant with black it makes sense to look at it beforehand, so that you know more about it than your opponent.

@tpr Okay, then how about some more common preparations, like the Veresov Attack (let's say you're trying to learn how to deal with the gambit for Black)? So the Veresov attack gambit line, the venomous London System, the suboptimal pirc, etc. Also like all the gambit lines you might face (The Sicilian Wing Gambit? Yes you'll barely ever face that, but what if the player's rating was higher than you? That one extra win would be rewarding).

In what percentage of your games are you going to get mainlines and good opening positions? I would say about half. Therefore I think if you're 1600-2000, there is some merit to studying garbage lines (Another example would be the Polish), and again studying the opening you play is something you should do anyway.

On the other hand, yes, endgames are the only way you're going to reach a title.

Frank Marshall studied his Marshall Gambit for 10 years, showing it to nobody. Finally came his day: he played it against Jose Capablanca in the New York 1918 tournament. Capablanca refuted his line over the board.

#12

Hey, it's that video I requested...

#63

The funny thing about the Marshall Gambit is that Aronian's line is basically a draw, when Marshall was a big attacking player.