Build it individually. That way you will have exactly what you want, and you will have all the tools and know how to repair or upgrade it as needed.
Dude, not sure how you did it but it took me a few builds to realize that I should take my time and get what I wanted. My fist build was build the lower, buy the complete upper then I gradually got to the point of just getting the parts I wanted.. I think there is a progression everyone goes through.
Eventually you have an idea of the perfect rifle and you build it.
Took me four years to get there.
If this is the first build, good luck and wish you the best. It is an addiction and you will get to the point where you want the drop in trigger, larue quad, vltor charging handle, nic boron bcg and so on.... Enjoy your build and wish you the best