is this correct on string of nouns you need and before the last one.

On adjectives you do not?

These sentences below are incorrect:

incorrect Helen is bright, friendly, and confident. ( take out and)

We have many dogs, cats, lions. (put in and)

2 answers

Yes.

Writeacher is much more experienced than I am in many of these grammatical rules.
Series of nouns
http://grammar.ccc.commnet.edu/grammar/commas.htm
See #1 for series of nouns.
See #5 for compound adjectives.

HOWEVER, when the compound adjectives are at the end of the sentence, use a conjunction.