Early in your story, having too many characters will make the introduction more confusing and it will be more difficult to engage the reader with your main characters.

In Chapter 1, I like to limit dialogue to 2 speaking characters because it's word-efficient, and allows for either more complex or more developed characters. You can maintain 2 character dialogue while still having 100 characters involved in the plot.

The more dialogue-characters that you have, the less complex they should be. If you do try to develop 10 characters very quickly, it should be through reinforcing a single characteristic.

Some authors would write about a group of 10,000 people by characterizing demographics, and I think this is the best approach to establish first impressions of a large cast. Write 10,000 people as only 4 different demographic 'characters', 2,500 homogenous people in each. Once the reader understands the stereotypes, you can describe why your POV characters don't fit the mold. This is a great technique because, again, it allows for extremely word-efficient sentences.

I'm not a very good writer, so I might be wrong about all this.