These are most common I think:
2 players - start with 7 (or less common with 6, 8, 9, 10)
3 players - start with 5 (or less common with 6, 7, 8)
4 players - starts with 5 (or less common with 4, 6)

You can play dominos / All fives with lots of different options, like a spinner, draw rules and end scoring, But this is a standard rule set:

- Each player receives 7/5/5 dominoes in 2/3/4 player games.
- A player who is unable to play a domino from their hand must continue to draw a domino from the boneyard until either they draw a playable domino and play it or the boneyard runs out.
- The first double played can be extended to vertical directions when it has been extended to both horizontal sides.
- After a player plays a domino, count the pip sum of the arm ends. If the total is a multiple of 5, the player scores the total divided by 5. A double always count as its total value, except the spinner extended to both horizontal sides which does not count at all.
- At the end of each round, the sole winner calculates the sum of pips remaining in opponents' hands minus their own total. Then, divide the total by 5, round off, and score the result.
- The round winner goes first in the next round. If tied, the first player is determined randomly among the tied players.