There's a lot of room for selfishly being "selfless." Rand tends to make strong points stronger by reappropriating words. It took me a long time to appreciate what she means by selfishness which mostly amounts to you not owing anyone anything (ie you aren't born with social/societal debt).

(You are both referencing her as intended but I wanted to elaborate in case anyone might be as confused as I was initially.)

I haven't watched the last week or two yet.

what's the best material (Fountainhead and Atlas excluded) to learn and put into practice Objectivism?

I read about natural law for many years, but it really had little in common with my law practice. I defended people accused of crimes in the U.S., so of course I had to focus on the U.S. constitution and the bill of rights. The U.S. was founded on the English common law system. There is a slight overlap there with Natural Law as I believe you mean it, but not much. Of course my purpose as a lawyer had to be to work within the system, while always hoping the system would change.