A box of 12 “Day & Night Toddler" Pampers in the purple box. This was probably when I was about 18 and finally able to drive, and had a job and some of my own spending money.
Up to that point, for years, I'd done the “towels and trash bags” thing, sometimes instead of towels (which were kind of rough on one's wet “nether regions”) I'd instead fold a thin, single-bed blanket into a nice, soft bulky diaper. But for “plastic pants” it was always the same--a white “Tall Kitchen” sized trash bag, I'd cut leg holes and as I was slipping them up my legs I wrapped vinyl electrical tape around the openings which served as “elastic” and kept them tight and prevented them from tearing. After getting them up all the way I'd also wrap tape around my waist then cut off the excess bag and voila! “Plastic pants!”
This was a dangerous thing to do because I still lived at home and had to hide away my wet towels / other items until both of my parents were out for a while, then I'd quickly wash/dry them.
But once I had some money, I discovered Pampers. Honestly, I think this happened on a night when I'd had a big fight with my girlfriend. I was then very much into the “binge and purge” thing and this coincided with my relationships with girls. When happy with a girl, I generally didn't wear my diapers but if we had a fight or broke up then “Hooray! I can wear my diapers again!” Then I'd get that out of my system, feel bad, often throw away my baby things, then back to my girlfriend (or a new one).
Well, one night we'd broken up and I was already thinking about diapers and stopped at a drugstore for a few things and when I saw all of the Pampers I very excitedly bought a box.
And that began my “disposable era” which lasted for about five years until I finally lived on my own, it was much easier to get rid of a bag of wet disposables than try to wash cloth items at home.
Once I lived on my own, I started buying actual cloth diapers--somebody used to make large toddler prefold ones that were 24" x 24" that fit quite nicely--I'd eventually get some of the smaller oblong ones with the soaker pad strip in the middle and put those on the inside. Also, I was still small enough that I could barely fit into the largest size of the Gerber plastic pants for a while. Then I met the wonderful girl who is now my wife who could sew, and she started sewing me adult-sized diapers out of the toddler ones, also we bought baby vinyl at a piece goods shop and she made me REAL plastic pants.
Also during my “disposable era” I discovered Amber Enterprises run by “Mommy Florence” and ordered several of her adult baby books and newsletters, and she also offered a few photo sets of pretty girls in diapers.
But those were the first things I ever bought--after improvising and making my own “diapers” and “plastic pants” for years.