Guidance on dyeing cotton t shirts with least amount of materials

Hi all, I'm trying to dye white t-shirts into decently naturally colored shirts.

I was thinking of things such as coffee and green tea to start since I assume I just need boiling water and the coffee / green tea.

I was thinking of going to the dollar store and getting either in a large quantity such as 20 bags of tea per shirt to make sure the green tea makes a decent impact on the color.

Any other advice or suggestions on the natural source of dye would be amazing. Just trying to make a noticeable difference with the least amount of work

Thank you