Extracting the followees (friends) of a list of users



I’m working on the topic of News Recommendation for Twitter users.
I use the Streaming API to get the Sample Tweets from Twitter, including for each tweet the id of the user who publish it.
Unfortunately, the Streaming API doesn’t seem to provide the informations about the user, especially the list of its followees.

So after extracting the tweets during a certain period of time, I have tweets from many many users.
I would like to get the list of followees from each user. I use the REST API…
As I am limited to 15 requests of that type/15 minutes, I guess I can only get the information for 15 users per frame window.

I would like to know if there is a way to be faster.