So I took the plunge and picked up an M&P 15 OR on a good deal. Of course this model comes with no sights at all, it has a railed gas block. I'll add a red dot at some point but for now I just want some basic fixed or flip-up sights. I'd rather not invest a whole lot until I get some experience under my belt. Can I get front and rear sights for around $100 or less? I was looking at the Magpul sights but they recommend not installing the front on a gas block. Or should I just spend the $200+ and get Troy? I know this is pretty basic stuff for you seasoned ARers but I'm new to all this. ARs are almost too configurable. You can go crazy thinking about all the options.