as a mid range & low range android device user i can understand the frustration of “insufficient phone memory” error. previously i was using xperia C which was limited to 1 GB system storage, initially it was but with time after some of the apps received updates my phone’s internal memory went low.
i tried many memory cleaning apps & tricks but non of them worked. one day while searching for solution i found an app and decided to take risk to resolve this issue & it worked for me. and i hope it will help you too resolve low memory issue on any android device. by using this method you can remove system apps & then reinstall them on your sd card.

You may follow this process at your own risk, deleting or modifying system files might be risky.

1. Before you start take a complete backup of your data & stock recovery using CWM or titanium backup.
2. your phone must be rooted. (may void warranty claims)
3. Class 4 and above SD card for phone.
4. Download “system app remover ” from play store , (if there is not enough space, you can temporarily uninstall updates of some apps. e.g. Gmail, Maps, Google Search)
5. Most tricky part is now to remove the apps you don’t need, in my case, Facebook, Office suite, walkman, trackID, were pre installed in my phone, which i have hardly used & worst part was unable to move them to sd card.
6. Open system remover app brows through menu and tap on system apps. as you can see in below screenshot it will show you suggestion which apps are safe to remove, but be careful, i would never suggest you to remove Google apps , as it may generate error which might not be resolved.

my suggestion is select one app at once and see the results, if any error pops up you can restore that app by going to recycle bin from menu. but once you restart phone, that app will be removed from recycle bin (in my case it was not there)