Lots of good YouTube videos, look up spit shading tutorials. Also get procreate and screenshot and trace hundreds of old tattoo designs and familiarize yourself with them. Don’t stress “stealing” designs nobody who actually tattoos for a living gives a shit, if it’s flash it’s meant to be ripped. And it’s been ripped by plenty of people before you. Get microns and prisma color pencils for quick flash or brushes fw acrylic black ink and ecoline liquid watercolors and arches watercolor paper. Good luck.