How much money should i save while in the Army?

im joining the Army in august, hopefully as an E-2.. which is about 1600 a month. Im going to buy a car, like a used trail blazer or something, and im going to have a cell phone bill, say $150 a month.. so that will leave me with $1000 a month for anything I want pretty much.. after i get out i want to move to NYC get an apartment and become a police officer.. so Im going to need money for furniture and the apartment until i can get a job, and all that good stuff.. so what should i save while in the Army? I was thinking $500 a month, but I don't know if id be able to live off $500 a month for 4 years, or until i get promoted and get more money..