In positions like this (while the a1 rook is undefended), a typical plan is to play immediately 1...b6 and reply to 2 b4 with 2...a5, the idea being that white cannot defend the b4 pawn with a3.
In order to analyze the consequences of this plan, I'd check the following:
- bxc5, dxc5 would give black's bishop the long diagonal and should be preferable for black
- cxb6 axb6 (or cxb6) does not seem so clear to me, because the light squares on the queenside get weak. Assessment might depend on whether black can take advantage of the half-open a file and/or can put his queenside pieces to good squares without giving white too much play on the light squares.
- ...b6 2. b4 a5 3. b5 Does not look attractive for black
So it seems that black does not get anywhere on the queenside, which leaves the pawn break with e5 as the most reasonable alternative. The idea would be to either open the long diagonal for the bishop (if white captures on e5) or to create a weak pawn on d4 (if black captures exd4, exd4).
There is not much white can do to prevent black from playing e5 sooner or later. The next white moves are pretty much predictable (develop pieces, castle, push pawns on queenside...). The question is how black wants to prepare e5.
- ... a5 is probably a good idea because it hinders white's natural plan of pushing the queenside pawns
- c6 vs Nc6: the pawn on c6 would protect d5 which could be important after white captures dxe5; The knight on c6 looks a bit unnatural, particularly if white manages to create a pawn storm. On the other hand from c6 a knight could put pressure on the d4 pawn.
- Bg4: with all white pawns on dark squares, this bishop could be strong. You might not want to exchange it too soon.
- Re8: probably a good square for the rook
Taking into account all this and potential tactics such as white sacrificing a pawn on c6 (if black plays Nbd7), etc, I believe the best options are:
- Re8, Nc6, e5
- Re8, c6, Nbd7, e5
- c6, Nfd7, e5 (but black might delay his development too much here)
ALl of these could be combined with Bg4 depending on how much you value bishops vs knights. Personally I'd go with the Re8, c6, Nbd7, e5 plan