Benoni Repertoire

I want to play the modern benoni for black, but i'm not sure to do after like 2.Nf3 or 2.e3. Any suggestions?

You could play 2...e6 or 2...c5 right?

Get GM Reperotire 11 and GM Repertoire 12 from Quality chess.  12 will take care of the Modern Benoni, 11 all the other junk.  GM Rep 11 accounts for 1...d5 players and 1...Nf6 players, so there's something there for everyone.

1.d4 Nf6 2.Nf3 c5 either leads to Benoni or an even game and 1.d4 Nf6 2.e3 c5 leads to either a double Tarrash pawn structure (e3, d4, c4 vs e6, d5, c5) or simply an even game if White opts for a e3, d4, c3 pawn structure.

If you get into a Colle setup I recommend NEVER playing e6 and instead try g6:

What else is there?

White can try a lot of things: g3, e3, and c3, to mention a few options.

Maybe 3.d5 e6 4.Nc3

Yes, white can try that.

On 2. Nf3 or 2. e3, my recommendation would be to just go for a classical queen's gambit declined with 2. ... d5.

I don't see it. 3.g3 cd 4.Nxd4 e5 5.Nb3 d5 looks fine to me and after 3.d5 e6 4.Nc3 ed 5.Nxd5 Nxd5 6.Qxd5 Be7 Black can castle, play Nc6 and Be6 and be home free.

3.g3 cd 4.Nxd4 e5 5.Nb3 d5 6. c4 looks playable for white, as does 3. d5 e6 4. Nc3 exd5 5. Nxd5 Nxd5 6. Qxd5 Be7 7. Bf4.

i think you can play c5

Yes. c5 retains some more options.

Either leads to benoni or slightly better game for black?

Doubletrade on d5, play Nc6 followed by d6 and Be6 with equal chances (Attack with Black)

2.. c5 is okay, it is 1: d4 c5 which is inferior.

Starting Out: Benoni Systems, which covers various Non-Modern Benonis, talks a lot about 1.d4 Nf6 2.Nf3 c5.  It also covers lines like the following:

- Benko/Volga Gambit
- Schmid Benoni (1.d4 c5 2.d5 d6 - I had one of these as White recently by transposition and won)
- Czech Benoni (1.d4 Nf6 2.c4 c5 3.d5 e5)
- Closed Benoni (In essence, a Czech Benoni that started 1.d4 c5 and White specifically does NOT play c4, and instead plays an early Nc3 - Another I had as White recently and won, and the Closed Benoni has FAR LESS respect and success compared to the Czech Benoni
- Snake Benoni (A modern benoni with Bd6 instead of d6)
- 1.d4 Nf6 2.Nf3 c5 systems, like the Psuedo-Benko (3...b5), or Psuedo-Modern (3...e6).  Neither is particularly good for Black if White doesn't play c4.

Also, based on another post, After 1.d4 Nf6 2.c4 e6 3.Nc3, you are not forced into a Nimzo or QGD.  You can still play the Modern Benoni with 3...c5, but you then must be willing to deal with the Flick-Knife Attack (also known as the Taimanov Variation, the line where White checks on b5 on the 8th move).  Many players dread this line, and so by choice, they only play the Modern Benoni against 3.Nf3 or the Catalan, and not against 3.Nc3.

Thanks everyone for your thoughts. I think I will just play 2...e6 to have white commit to his setup first.