Quoted:
I’m building my first Ar15 and I have a Kaiser Defense lower complete but I’m not sure exactly how to build the upper. I have a DD barrel and looking to get a DD upper and troy rails, but not sure. I'd stick with DD and get the Omega - personal preference.
Dose the gas tube come with a gas block? if not where should I get one? Not usually unless it is specified.  You will need a roll pin, also.  PK Firearms, Midway, Brownells, etc.
Do the nuts that hold the barrel to the upper come with the rails? If not where should I get them?  It depends on the rails and model.  Once you pick the rail you can figure out what you need.  Some come with everything and some will need a standard nut, others will need a standard nut and Delta Ring Assembly.
How much torque should be used? What kind of wrench should I get?30-80 ft lbs - tighten/loosen three times, torque until the next gas tube slot aligns.  Read the build it yourself  tacked thread for more info.
I like DD but is their Bolt Carrier Group Assembly all I will need, or do I still need to get a firing pin? (You guessed it) if not where should I get one? A complete bolt carrier group will come with it.  If you want an extra look at the same places above.

I know I ask a lot of questions, but help with even one will be very much appreciated.