I have a Xperia E1 with 2Gb of internal memory. I had to buy an 8GB SD card to use good apps! The problem is that I can only use 2Gb of my SD card on apps! When I open the storage it say it has 6.90Gb free, but when I open from Apps settings and check on SD card it say 505Gb free.
It is because since older versions of android(i don't remember which exactly) its not possible to install or move apps to SD CARD without root.
All apps will be installed in internal memory by default however if you do root you can move them to your SD Card using apps(there are many) and at same time you will be able to delete useless pre-installed apps that is using your internal memory space.
Also i just noticed that u have 370MB of cache data, that data is near useless, since its just used to make things load faster but eventually it start to use too much space on your drive so you can safely delete the cache of all your apps, you can use apps for that...I use Cache Cleaner
According to Sony's Xperia E1 specifications page, you're running Android 4.4, KitKat. As mentioned in numerous SE articles, KitKat does not allow the SD card to be used for app storage, including transferring apps to it. Sony's page does say you can add it, but unless they hacked KitKat, it won't work.