Procion fiber reactive dyes applied to plant based fabrics. Presoak in a sodium carbonate solution as a fixative. Allow adequate time for the chemical reaction to complete itself, at least 12 hours, but 24 hours is best. The fabric must stay damp for the reaction to exhaust the dye, so if you have a dry climate, create a humid one or use plastic to prevent moisture loss.
Marketing is dependant on what venues are easily available to you. Festivals are work intensive, but can be very lucrative. Good luck with transforming your hobby into an income.