How markets in the poorest of countries revolve around circular markets working on about $1/day.
Is there such a country that lives on just $1 a day? I live in a third-world country which I consider to be a poor country and the minimum wage here is at $10 a day.
People with such low income should keep saving in fiat until it is big enough to engage in Bitcoin transactions. Saving one dollar per day in a month could give about $25 worth of Bitcoin. An individual could also seek alternative sources of income so that he would have more funds to use Bitcoin.
I also doubt they would bother to buy and own bitcoin. As a poor individual, your priority is to survive through the day. You will prioritize being able to buy food and pay bills rather than buy bitcoin. Most of them don't plan to have investments and contented to live what they can afford.