BariqWani
Keep all your riders satisfied with their number of orders. You can do this by limiting the number of hires.
Take the average orders per day for last 30 - 60 days then divide it to your number of riders. If the result is satisfactory according to your country minimum or a little bit above wage, then your number of riders is fine. Adjust according to that.
Letting them choose their own time is hard, what I did is I selected the best rider, gave him a better rate in exchange of making good and fair scheduling for all riders. 😀