I’m pretty sure we’ve all got at least one gadget we bought for a gun languishing in a box somewhere where we hope it will never be discovered. The modular nature of the AR15 is a big contributor to this as is the tendency to always want to have the latest and greatest gizmo attached.
The first thing you should do is ask yourself “why am I getting this?” If what you have works you probably don’t need it. If it’s to help you shoot more accurately I’d suggest range time. That’s not to say you shouldn’t get a light, laser or good sight for your pistol. Or that optics for a your carbine are not a good idea. Just that you should be sure why you’re buying it before you do.