Gambits. What to do against them?

"The best way to refute a gambit is to accept it" Wilhelm Steinitz. They are usually sacrificing material for some kind of a positional advantage or a promising attack and they vary widely depending on the position so there is no universal approach against them.

As a side note I would argue the Queens Gambit is not actually a real gambit aside from its name. Taking here can lead to more trouble than it's worth.

Just because there is "gambit" in the name it doesn't mean that it is some opening trap. The King's Gambit, for example, is a rich opening with thousands of pages of theory. Good luck "learning to counter it". The Queen's gambit isn't a gambit at all (Black can't keep the pawn), it's just a normal opening.

You should not study openings at all. Follow opening principles ( a simple google search will show those if you are not familiar with the term), look out for tactics, and you will be fine. Worry about openings when you have a rating of 2200.

Take the first pawn, leave the second. As others have said, a Gambit isnt a trap. Your opponent is offering you a material advantage in return for a time advantage. Keep calm and calculate. Take the pawn, develop quickly, castle to safety, and meet their threats.

In the Queen's Gambit don't take, defend d5 with a pawn. For any other Gambit you can take a pawn, but if they offer you a second one you should refute it. When you accept a Gambit you should try to develop actively and trade pieces when you can

Taking the pawn in the Vienna Gambit is basically losing on the spot

You can't really hold on to the pawn in the Queen's gambit

Kings gambit is best to just take, but there's a lot of theory in it as well

In the Vienna Gambit you could move your queen as black to e7 (4th move). If opponent plays queen e2 then move your pawn forward to f3. 

You could even go Ng8 white doesn't have anything concrete here.

It's still losing. Don't accept the Vienna Gambit. 

Ng8 is an expected response. You're going to end up behind. The best answer is to just not accept the gambit. If you are facing it, move your d pawn. 

True I have won like 60% of my games as white but still if the opponent is really good we can lose. I have messed up some games. Vienna Gambit is really good. 

I hate the Kings Gambit as Black anyway. I like playing the KID (it is my favorite opening) so I do not face the Kings Gambit very often.

Behind in what? Development? Space? Black seems perfectly fine if he knows what he's doing. The database seems supportive as well.

That is incorrect. The position may be playable but white gets the center with a lead in development.

I probably accept every gambit I face except for the queen's gambit

I'm sure if you decline the king's gambit you will also get some free wins lol

lol, apparently this is a countergambit

My generalised suggestion would be if they are giving you a pawn,  take it. But, if they give up another one, then don't take it. Don't accept the second one. 

Usually, I don't take the pawns. Instead I develop pieces and keep the tension. Always try to maintain the centre pawns. 

It's advisable to not give up your centre pawn for a flank pawn. 

Huh?

I disagree, one of the main moves in the d6 or even the nc6 sicilian is d4, trading a center pawn for a flank one, but giving the knight a comfortable square in the center.