You can probably save at least 2500. Given that you are in sharing accomodation, you can pool your food expenses which would mean about 200-300 per month. The remaining 500, you can spend it for yourself. Leaving and working in Doha is a sacrifice. To survive, you need to treat yourself, once a week is my suggestion, and you can use this 500 for this purpose. Go to souqs, corniche, malls and eat nice food - once a week. Good luck my friend.