I too do mostly city driving. My commute is about 5 miles, and takes 15, sometimes 20 minutes, depending on traffic. I've averaged 43mpg over the past year.
Everything Eggman said is right. Everything.
Light foot is the way to go for good economy, along with keeping your eyes down the road, anticipating when you can let off the gas and coast to red lights.
View my fuel log 2015 Mirage ES 1.2 manual: 44.0 mpg (US) ... 18.7 km/L ... 5.3 L/100 km ... 52.9 mpg (Imp)