You can leave cache alone, as it is safe and manages itself. Cache is a temporary storage for your phone to access everytime you open an app, that is stored there for future use. So, if you use maps, for example, your phone will find your location. Then you tell it where you want to go. Then go from there, and so on. Your phone will store your Maps cache (ie: your location, City, etc) for next time it's used.
This is so that your phone doesn't have to work as hard to power up the app, start up a location search, etc. The app cache remains at a standstill till you use the app again. Also note, that your phone will remove any files that aren't being used automatically. This is so that it can make room for other programs.
Clearing out cache just make your phone have to work harder, drain your battery more, and make you wait longer to open/use an app.