My first ever collection was a stamp collection when I was about 10. I think it was prompted by my class teachers who encouraged everyone to have a hobby and share it with the class. I managed to fill up an entire album, but most of the stamps were store-bought. So I'd had stamps from Bulgaria and Venezuela, Papua and Lichtenstein, countries that meant nothing to me--that I could never point out on a map, if my life depended on it.
Then I moved on to coins, but that was short-lived, as foreign coins were much harder to get hold of. I also collected bookmarks, key-rings, candles until I ran out of space and realized that they didn't serve much purpose except to attract dust like moths to a flame.
Finally I settled on postcards, as they have a much more sentimental value, and you don't need a magnifying glass to enjoy their beauty. My mom already had several old postcards from her brother-in-law who sailed around the world, so I used those to kick-start my collection. Right about then, I had also started having penpals, so my postcard collection steadily grew.
Now as I travel abroad, I would buy myself postcards as souvenirs, instead of the usual knick-knacks. Whenever my friends holiday abroad, I bug them to mail me some.