You are fine to assemble most parts without additional oiling. The upper and lower match up don't need oil.
The Bolt Carrier Group needs to be well lubed. A little on the buffer and buffer spring is good, but not absolutely necessary.
A very light touch on the hammer and spring is a good idea, but don't hit it with excessive anything ( soap, oil, filing, sanding. or any other form of love ).
You'll be fine, just follow the build instructions and everything will go together just like you plan.