Hay if you want to get started on some graffiti designing  for the fist time Spray paint is obviously the number one supply you need for graffiti. You can buy them at any hardware store or graffiti specialty shop (more expensive there though). Also, legal or not, I suggest disposable gloves because paint on your hands can be tedious. I suggest starting off with some cheap paint to see if you really have a desire to do graffiti before you invest a lot of money into it.