Welcome to Ecomodder!
I think you can hit 50+ mpg easily, and 60 MPG if you're careful. My last car, an 04 civic sedan, was able to average 45.8 MPG during the time I owned it, with many trips in the 50s and one highway trip just barely hitting 60.0 MPG with a tailwind (verified at the pump). Mine was an automatic, which is about a 10% FE handicap compared to a manual, so you have an advantage there.
Here's the link to my build thread to see what I did with mine:
http://ecomodder.com/forum/showthread.php?t=36160
Note that the "70 mpg" trips claimed on some posts turned out to be false when verified at the pump - the Torque app overestimated around town fuel economy by about 20%, and underestimated highway fuel economy by about 20%.
Pump up those tires, but don't run over 60 PSI. 68 PSI made my Civic a little squirmy on concrete highway in strong winds. An inconspicuous air dam was worth a couple mpg. Lighter rims + narrower tires was another mpg or two.
Those 7th gen Civic are sweet cars.