As Aquila pointed out, that phone is very limited on space to begin with, and chances are you will be fighting storage issues no matter what you do.
The OS is likely taking up the majority of the space. Without seeing a screen shot of how your phone breaks down the storage allocations, I could only guess at what "miscellaneous" is. It could be cached data, texts, themes, etc.
But still, apps and data use in general are growing steadily. Just a few game apps today could eat up any free space you have even after a factory reset.