What tax files do I need for form 3520?

I am a U.S. citizen married (filling jointly) in California and received a foreign gift in the 2016 tax year. My CPA says he needs my W-2 and paystubs, but I don't think that is true. I believe the form 3520 is purely an informational form only and not part of a tax return.

Can anyone confirm this statement? Also, what are the best ways to avoid getting taxed on this (this was a gift)?