How important is the dragon bishop?

This is a game i played as black. 

I tried to take advantage of the fact that my opponent didn't play f3 and captured white's dark squared bishop.

But it didn't work out at the end.

Please provide your suggestions

I guess that you should have tried to keep the bishop pair. Black has no black-squared bishop, while you do, so you have more opportunities to attack on the black squares. When you exchange all of your bishops, white is better, because he has a powerful attack on the f-file.

14...Ng4 is a tempo gaining move that opens up the dark square bishop. I also like the idea of 15...Bd7 this gives your rook the ability to enter the game is need on the open c file. But I really dont like the idea of moving the king earlier and sacrificing your castling rights that alone might have been the losing point.

Why did you play 8 Kf8 ?
after the simple B or N d7 black has a good game. 

The dark square bishop is one of the most significant piece in this defense, particularly for black, who often sac an exchange instead of exchanging it.
White's dark square bishop is needed to fight black's and trying to exchange it. 

E-D-W : Ng4 serves no real purpose. Also the knight is well placed on e5. 15. Bd7 seems a good move, thanks

AngeloPardi : B or Nd7 will lose a piece

Well, I don't know the book.  But going into a variation where you're forced to give up castling certainly doesn't seem right to me.

7... Ng4 is wrong. After Qd2 you can play Ng4, because the queen no longer attacks the g4 square. But giving up castling seems bad, and white can still save the bishop.

Allowing white to take your dragon bishop means the entire plan was for absolutely nothing.

Well moving away the king instead of blocking was quite forced, after he played 7...Ng4?!. It does gain a tempo on the 6...Ng4? line though, so perhaps it's not too terrible.

Still can't be great though, and white should be better.

9.Bc1 seems to offer Black an ever darker future.

Your sideline at 22... is not clearly lost after 35.Rxa6, and anyways White's play was vasty suboptimal.

Yes 14...Ng4 is bad but 14...Nxc4 is winning.

I had this insane game

I was black

Looking at all the comments, very thoughtful.

Sent that inadvertently lol. I agree about b5 being irrelevant, as a tempo something but there just wasn't anything to address there, however I was thinking f5 might be a play to add pressure with your rook still buried about at least 3 moves behind all your pieces, as those pawns seem fit to both attack and defend, which might be an alternative tempo solution for you to consider.