Hello! Just purchased my first dslr-D3100 and so far I am loving it! It came with the 18-55 mm lens. I love to travel and would be taking most of my pictures outdoors. I love taking pictures of landscapes and of people. My budget is small and no more than $500 for the lens...is there any lens that would be a great "all round" lens for me in my budget? I would also be open to purchasing used lenses to save on money, is this pretty safe to do so? Worried that I would be stuck with something that has been dropped a few times and wouldn't work as well as new. Is it obvious to see a flaw in the lens?