I have a new SW AR-15 M&P Sport, I have only the rear magpul dual aperture sight. I really want to dress this up a bit. I am new to the AR world and need some recommendation/suggestions for a moderate priced set up. I cannot afford top of the line by any means. Would $300-$500 be a fair amount for such a set-up? And what are your suggestions. There are so many options, I have no idea where to start. Needs some hep please...