I love collecting stamps! It is actually one of the worlds most popular hobbies! 
You collect them by travelling or buying them?
I collect them by travelling. Hong Kong is a great place to collect stamps because it is such a common practice among retail outlets there! 
I collect coins. I assume stamps are pretty cheap.
That is pretty cool! Yeah I collect stamps because it is pretty cheap and it is fun to look at all the different types of photos on them, plus there is a never ending stream of new stamps
How many stamps do you have, and how do you store it?
I have over 500 stamps, I store them in my stamp binder, made specifically for stamp collectors. I love organizing them by country from where I get them because each one shows a unique historical and geographical aspect of the country on them.