Have you used the storage check - 2nd to last setting? as this will let you clean out your temporary files and move your maps to SD card. However if you don't have it download the beta from
Lumia Storage Check | Nokia Beta Labs
You will need to sign up, also you will need to clean out your internet explorer history individually, by opening internet explorer then ... -> scroll down to settings -> delete history. Best do this after you have bookmarked the sites you frequent but haven't bookmarked them.
I presume you are already using the SD card for pictures, music and videos?
Also once you install asphalt 7, would will need to clean out the temporary files.. for me it was 1 gig!