Recently bought a BCM BCG that is this one:

http://www.bravocompanyusa.com/BCM-Bolt-Carrier-Group-MPI-Auto-M16-p/bcm%20bolt%20carrier%20group%20auto%20mp.htm

What does not come with it that I will need to have my entire bolt assembly completed? Firing pin? I honestly have no clue, just want to make sure I get all the pieces on their way so I can finish the gun.

Thanks

The BCM BCG is complete (firing pin, extractor, bolt, etc).
If the only item you are lacking is the BCG, then your done as soon as it arrives.

Good to hear! Basically here are the minor things I am lacking. And you can ask more questions to see if I may be overlooking something.

I need:

Forward Assist Assembly - that is just Forward assist, spring, and roll pin I believe

Ejection Port Assembly - Cover Door, Cover Pin, C-Clip, Ejection Port Cover Spring - it just need one c clip? I think I saw something for sale that had a couple of c-clips. So that kinda threw me off.

Now I bought a Daniel Defense 16" barrel. What will I need for installing the barrel? Any specific barrel nut? Is there a specific barrel nut depending on what tactical rail/handguard I put on?

Edit: forgot to note I got a mid length barrel and don't have gas block yet or gas tube.

If you think I may be overlooking anything, or just want to question whether I have something, just ask and I will tell you what I have.

Thanks for the help!!

You really need to do some more research.  Check out the howto build an ar videos at brownells. They also have parts lists for you.   The list goes item by item what you need to order.  If you buy x part you dont need y but you need z and q.   That sort of thing.  Not trying to be a jerk... Its just that your latest questions are very basic and you should know them before even starting a build.   I just started myself so im not trying to act superior.  Just watch the videos and you will have 95% of the info you need.   The other 5% the people here will help with.

I know everything I need except for the barrel mounting stuff. Which I admit I don't know much of anything about. I know I need those "very basic" assembly pieces. But without fully seeing them in action and knowing their mechanisms regarding spring fuction, clip function, etc. it is hard to understand if there is an underlying piece that I am missing.

Read this and didn't know those videos existed. I found them and thought I would post the link here for anyone else looking.  Good stuff for us noobies!

AR15 Build Videos