If you haven't yet played Destiny, you might want to wait until the 20th of September, when Activision release the Destiny: The Collection.
This new version will include the original game in addition to the four expansions: The Dark Below, House of Wolves, The Taken King, and Rise of Iron.
Developed by Bungie and published by Activision, Destiny had an overall budget of $500 million dollars (including development and marketing costs), so it makes sense that they would release this new collection to try to squeeze out even more cash. It's already been criticized for its expensive microtransactions, but at least The Collection sounds like it has enough content to justify a full price tag. Check out the trailer below: