My tuppence worth
Get a polarizer for the 18-85mm (or whatever it actually is). A relatively wide-range "standard" zoom like this will give far more options on a day-to-day basis than limiting yourself to only having a polarizer for the 50mm.
Always use a lens hood. If you don't have one for any of the lenses, invest! It doesn't have to be a fancy "flower-petal" bayonet-fit hood, though they are very convenient to fit and dismount … a basic folding rubber screw-in hood will be as good for most occasions.
With a modicum of care (and a lens hood fitted), using a "protection" filter is simply introducing another opportunity to reduce image quality, either from distortion or reflections, unless you really are in an area where a high UV exists and is affecting your pictures.
Experiment with ISO settings. Find the highest setting where you are happy with the quality and don't be afraid to use it. From your remarks I get the feeling you're limiting yourself to a couple of slower speeds.
Keep Shake Reduction activated unless there's a good reason to switch it off, on a tripod for instance.
Push your limits. Take a lot of pictures then try to analyse why any one "didn't work" … wrong shutter speed, wrong aperture, wrong ISO? Once you've figured out what you or your camera/lens "can't" take, try to devise a way of doing it … even if it means upping the ISO and putting up with a bit of noise. It's surprising what the brain will accept if the subject matter is good! A "noisy" colour picture will often convert into a very acceptable "gritty/grainy" b&w picture
Good luck