In your budget, I suggest Suzuki Margalla as parts are readily available. But you may have to install after market AC for good cooling.
My parents owned this car and it was a pleasure to ride if kept in good condition.
If you want a car with a good mileage, you should go for Mehran or Alto. Used sedans are fuel guzzlers.
Our Margalla that was serviced monthly used to give 9 to 10 kmpl without AC.