i got a manga drawing book that has a storyboard thing inside, it’s pretty neat for writing a story
Manga Storyboard Sketchbook https://www.amazon.com/dp/1454929693?ref=ppx_pop_mob_ap_share
I'm gonna go against the top advice here: the kid's 8 years old, and an "all the things" art set is something that is probably going to be just fine for someone that age -- low quality materials and high selection is fun for a kid who is just starting their art journey, probably will treat them less like supplies, and more like toys, and do a lot of experimentation.
Also, if you were to get a "blank" comic book for him, I'd recommend pre-ruled, but not pre-boxed. Let him draw his own boxes. There's a great, inexpensive, and easy to find book that fits the bill wonderfully. It's called the Manga Storyboard Sketchbook by Sterling Publishing. If you wanted to flip through it, they're sold at Barnes & Noble, as well. While you're there, check out the "draw your own sticker" books, as well, which will probably be on the same shelf.
For instruction, my very favorite books are by Mark Kistler. Draw Squad and Imagination Station have corresponding shows from PBS back in the day -- Secret City and Imagination Station. Here's a playlist that includes some episodes of Secret City. and here's a rip of the first Draw Squad vhs. The books and shows are what set me down the path to drawing when I was a kid, and they're what I always share with the kids in my life. Kistler's an amazing teacher, providing valuable instruction, while being goofy and making sure fun comes first.