When should we use don't in a sentence and when should we use doesn't?
A few rich people doesn't make a country rich.
A few rich people don't make a country rich.
Which is the appropriate usage?
Normally, the verb agrees in number with the number of the grammatical subject, here, a few rich people, which is plural.
However, it is not uncommon that the verb will agree in number with the semantic subject, with an idea the speaker has in mind:
a few rich people paraphrase in context: the fact that a country has a few rich people
and in that case the number of the verb would be singular to agree with the thing the speaker has in mind.
In formal writing, we expect the number of the verb to agree with the number of the grammatical subject.