whats the best black opening strategy for a beginner?

As black you can't just say I will play the French defence or the Sicilian defence. Because it depends what white plays. For example, if white plays 1. d4 your French and Sicilian aspirations are unlikely to be helpful. You need a repertoire. In other words, you need a set of openings (rather than one).
But as a beginner I don't think it helps particularly to worry about what openings are called. Most beginners (so let's say this is people rated < 1000 on this site) will lose games because they don't notice that their opponent can capture their material and fail to take advantage when their opponent leaves material to be grabbed. So the most important skill to develop is observation, along with tactical awareness.
In terms of openings, my advice to a beginner would be simple:
1. Move pawns before pieces
2. Move knights before bishops
3. Don't bring the queen out early
4. Try to move each piece once only
5. Move central pawns before those on the edge of the board
6. Move your knights towards the centre not the edge (f6 and c6 as black)
7. Castle kingside and do it early
This is a set of principles that won't go far wrong.



As black you can't just say I will play the French defence or the Sicilian defence. Because it depends what white plays. For example, if white plays 1. d4 your French and Sicilian aspirations are unlikely to be helpful. You need a repertoire. In other words, you need a set of openings (rather than one).
But as a beginner I don't think it helps particularly to worry about what openings are called. Most beginners (so let's say this is people rated < 1000 on this site) will lose games because they don't notice that their opponent can capture their material and fail to take advantage when their opponent leaves material to be grabbed. So the most important skill to develop is observation, along with tactical awareness.
In terms of openings, my advice to a beginner would be simple:
1. Move pawns before pieces
2. Move knights before bishops
3. Don't bring the queen out early
4. Try to move each piece once only
5. Move central pawns before those on the edge of the board
6. Move your knights towards the centre not the edge (f6 and c6 as black)
7. Castle kingside and do it early
This is a set of principles that won't go far wrong.
While I agree with the overall advice of first learning to use the general opening principles before worrying about concrete variations I do find some of the listed rules little questionable.
Especially 2. I've always found to be of dubious value. I know it was famously stated by Lasker but this rule has just too many exceptions to be really useful imo. For example after 1. e4 e5 2. Nf3 Nc6 it would suggest we should play 3. Nc3 rather than 3. Bc4 or Bb5 and while the knight move is entirely possible both of the bishop moves are actually more popular (and Lasker himself mostly played Bb5).
I also think that 1. is missleading. Pawn moves in the opening are mainly good only if they are needed in order to develop the other pieces or help to control the central squares. If we could actually develop our pieces without moving any pawn that might be a valid strategy. For example 1. e4 is a good opening move because it achieves the dual purpose of allowing the Bf1 to move and gaining some central control.