Airline miles and points are made up by for-profit companies as a way to get you to spend more money with them. Don’t do it. Nothing is stopping them from deciding tomorrow that a billion points are now worth five cents. Get a Citi Double Cash card, which pays you actual money.
Good article from last week detailing how much airline rewards programs can change: https://www.nytimes.com/2017/06/12/travel/how-much-are-frequent-flier-miles-worth.html?_r=0