Move videos, pictures and music to a computer. Restart the phone. If you still don't have enough space, back up some of your larger apps (and move the backups to a computer) and uninstall them (then restart the phone).
You don't need cache cleaners - in Settings/General/Storage is a Cache line. Tapping that will ask if you want to clear all app cache. Say yes and all your app cache space will be cleared. (You can clear system cache in most recoveries, but you aren't using system cache to run Dropbox, so that wouldn't matter.)
07-30-2015 04:49 PM