At this point, you're probably used to buying pretty much anything and everything from Amazon. But once upon a time, you went to Amazon and entered your credit card for the first time.
And you might not know this . . . but you can find out what you bought that day. Go to Amazon.com, go to the "Your Orders" section . . . and you'll see a little dropdown box where you can choose to see your purchases from every year.
Pick the earliest year, and it'll show you the very first things you ever bought.
(Mine was some coffee and dog shampoo)