My dad actually bought a major set when I was 2. He always said he bought them for himself. I could use them qhen I was able. His 4-6-4 Hudson 773 with tender still sits on my fireplace mantle.
Got a basic Lionel set at 4, and a railcar, accessory, or more track for many Christmases afterward.
As a grownup with some cash, bought more Lionel. Still have it, converted my pingpong table into a trainboard.