— Chigorin systems after 2 Nf3 d5 or 2 c4 d5 (in the latter case you could always play 2...e5).
— know what to do if White plays 2 d5
— Nimzowitsch Defence after 2 e4
but you're right, you need to have an appropriate repertoire prepared if you're going to play 1 d4 Nc6 as Black. In my own games, 2 Nf3 has been the most common reply (over 50%).
After 2. c4 you also have the option to play the somewhat obscure 2...e5 lines, as NM jatait47 mentioned.
For example:
1. d4 Nc6 2. c4 e5!? 3. d5 Nce7 4. Nc3 Ng6 5. e4?! Bc5 where Black plays on the dark squares, with a potential to outpost on the f4 square later on. Black’s kingside is also particularly strong; and although the queenside is less so, White is lacking in momentum after the standard a3-b4 since Black has multiple retreat options as well as the d4 square, and the simple yet effective a7-a5.
5. e3 is more challenging but less often seen. Although there are multiple ways for Black to handle the position, I prefer the immediate 5...f5!? which regains some space and allows for counterplay on the kingside. The soundness of this option is questionable, and is just my preference. Though there are other ways to continue, such as 5...Nf6, 5...Bc5, 5...d6, etc.
——
Nc6 against d4 used to be my go-to, but I accumulated a dislike for the 2. d5 lines, partly because I personally don’t like trading Queens early, which seems to be a common theme, like after 2...Ne5 3. e4 e6 (3...d6!? is an interesting idea, I suppose) 4. f4 Ng6 5. dxe6 dxe6 6. QxQ KxQ where Black seems fine, but the game is without Queens. 
5...fxe6!? is an alternative I suppose, but the weakened kingside does bother me. The 2.Nf3 lines also gave me trouble because I don’t know Chigorin Defense theory.
But if these factors don’t bother you, then by all means, it is a pretty decent defense!
After 2. c4 you also have the option to play the somewhat obscure 2...e5 lines, as NM jatait47 mentioned.
For example:
1. d4 Nc6 2. c4 e5!? 3. d5 Nce7 4. Nc3 Ng6 5. e4?! Bc5 where Black plays on the dark squares, with a potential to outpost on the f4 square later on. Black’s kingside is also particularly strong; and although the queenside is less so, White is lacking in momentum after the standard a3-b4 since Black has multiple retreat options as well as the d4 square, and the simple yet effective a7-a5.
5. e3 is more challenging but less often seen. Although there are multiple ways for Black to handle the position, I prefer the immediate 5...f5!? which regains some space and allows for counterplay on the kingside. The soundness of this option is questionable, and is just my preference. Though there are other ways to continue, such as 5...Nf6, 5...Bc5, 5...d6, etc.
——
Nc6 against d4 used to be my go-to, but I accumulated a dislike for the 2. d5 lines, partly because I personally don’t like trading Queens early, which seems to be a common theme, like after 2...Ne5 3. e4 e6 (3...d6!? is an interesting idea, I suppose) 4. f4 Ng6 5. dxe6 dxe6 6. QxQ KxQ where Black seems fine, but the game is without Queens.
5...fxe6!? is an alternative I suppose, but the weakened kingside does bother me. The 2.Nf3 lines also gave me trouble because I don’t know Chigorin Defense theory.
But if these factors don’t bother you, then by all means, it is a pretty decent defense!
i really dont trust 5...fxe6, they are so many lines for white like, a solid e4-f4 nc3, g3 bg2, qe2 formation which just leave black with a funky looking light squared bishop or one of two knights on the kingside looking silly. 6.h4! is also not pleasant
i used to hate the prospect of the queenless endgame, but black actually gets some pretty interesting positions out of it, most often, black will play, bc5, bd7, nh6, f6, nf7, e5. although rarer white lines may demand, bb4 or bc5 and nf6. GM Stevic is a 2600 with an amazing record on this queenless line.
Wow, so great to see this post, especially on such an obscure opening. I've been playing 1. Nc6 against everything for the last few years, so I'm pretty much an expert on it, hopefully I can help here.
There are pretty much 7 different setups you need to know, I'll go through each of them.
1. The 2. d5 push
Model Games: https://www.chess.com/game/live/32528441447
https://www.chess.com/game/live/32614825851
2. C4:
3. e4
https://www.chess.com/game/live/31114181727
4. 2. Nf3 d6 3. d5
https://www.chess.com/game/live/31300779255
5. 2. nf3 d6 3. e4
https://www.chess.com/game/live/32533851385
https://www.chess.com/game/live/31220361665
London Setup
Hey fellas, intermediate chess player here, I was wondering how many openings I would need to know if I play 1.d4, Nc6 as black? Would be nice to be able to play into something because every opponent only plays the chigorian against me (p.s. i know how to play the budapest.)