The reason your friend had trouble with his NCstar is because it was an NCstar. You might as well just throw your money in the toilet and flush.
I, for one, can't afford to spend $5-600 on an optic, even for my very custom DD, piston converted SBR. Not to mention, I just don't see the point. I don't rely on this gun to defend my life day in and day out. If I was going to war, id spend big bucks on an optic. For the range and 3 gun stuff my Vortex optics have all been great. I have a sparc now and really like it, I've had about 8 Srikefires and they were hit or miss. Some were awesome, some needed to be replaced quickly. That said, Vortex was awesome for replacement. Thought they weren't overly fast. I find a 1-4 optic to be my personal preference. A Bushnell AR optic is a good choice. I have one on my DD right now and its been excellent. Holds zero, its very clear, great features for the money. I had a Vortex 1-4 that cost more than double what my Bushnell cost and it wasn't any better IMO. Burris makes some good choices as well. Their Fastfire 3 is a great optic for the money. VERY small but works excellent. And their line of 1-4 tactical style scopes are great.
If your going to upgrade your Norc but plan to build a better gun down the line, consider buying parts for the norc you can eventually switch to the other gun. For instance, a stock. Sure, it may not be a huge deal but your going to want a good stock on your custom gun. So buy the one you'll want down the road and put it on the norc now. There are also lots of stocks and grips that aren't expensive but are still good. Magpul MOE stocks come up often on the EE for around $50. They may not be as good as a CTR but theyre better than the factory Norc stock IMO... I hate those ones.
The fore end is another story. Good ones cost quite a bit. Cheap ones are cheap. You can always put a cheap one on your norc now and get a better one for your new gun later. There are lots of reasonably priced rails out there that utilize the factory barrel nut so all you'd need to do is cut off the delta ring with a dremel and either shave down your A2 sight, or replace it with a different gas block (pretty easy to do at home) OR get a rail that goes around the A2 sight... which may require just cutting the delta ring off. OR, you could get a magpul for end that offers many rail options and looks pretty nice. They are drop in. If you match up all the magpul parts on the gun it can actually make it look pretty sweet. Even a norc.
I do agree with the other posters though, don't buy new stuff. The EE is FULL of great deals on barely used guns and parts. No point in throwing your money away unless you absolutely MUST have a certain part you can't find elsewhere. Even when you plan to build your own gun, you could look on the EE for a good staring platform that has the base components you want and just upgrade it from there. I started with a used but basically new DD M4V5 and have changed nearly everything on it. But I used the parts i took off to build other guns that I sold to recoup my money. And, it was fun. Now, I have my personal idea of the perfect AR.