Check out what others in the "Garage" area get:
https://ecomodder.com/forum/emgarage...=Search+Garage
low to mid 30's seems pretty average, some in the 40's and one nearly hitting 60! So yeah, i'd say your goal of 30+ city should be pretty easy to obtain.
For city driving with plenty of traffic, neutral coasting to each stop is going to be critical. Learn to read the lights and memorize the timing and order the best you can per. Learn to hit those brakes early when you know a stop is coming up and think you can keep rolling as the light turns green and traffic will be moving (not always predictable, but always worth a try).
Mod wise, air up those tires! That's an easy one with the lowest risks and is easy to do. Depending on your speeds is weather investing time and money into a lot of aeromods will pay off. Even 30mph speeds benefit, though.