Since I don't really feel like there are resources out there for what to buy, I wanted to share what I recently purchased from Paper & Ink Arts. I'm still in the process of learning Calligraphy so that's why I bought these books, and just skimming through the first few pages I've already learned a lot.
The titles of the books are American Cursive Handwriting & Ames Compendium & Tamblyn's Home Instructor. Each of these books teaches you the basics like how to hold your pen and how to sit, and all have exercises to teach you consistency and movement.
I also bought a few different types of calligraphy pens: an oblique pen, two plastic pen holders that came with a pack of Speedball C nibs, two fancier holders, B nibs, a parallel pen, gouache to make custom inks, containers for those inks, Higgins ink, and materials for hand-lettering like a water pen, Micron pens, smaller paint brushes, brush pens, and a few Sharpies.