You have already bought a UV filter so there is really no need to buy anything else to protect the lens. For sunny days you should buy yourself a polariser filter - to give an example look at a holiday brochure and see how blue the sky always is, that is the effect of the filter. Like polaroid sunglasses it also cuts out the glare. You'll see a considerable difference in the quality of the image. Changing the U/V for a skylight might give a slightly warmer tone too.
The yellow "sepiaish" tone to your indoor photos is because you aren't using flash. If it is at events where flash is forbidden you need a better lens - there are many posts in the lens section on this for reference purposes. If permitted - turn it on, but don't leave the lens hood on or you'll get a half moon shadow at the base of each photo caused by the shadow of the lens hood. I know from experience!
Nice camera you have. Enjoy.