Interesting Question?  I have an advertising agency also, so have knowledge for not only us -- but for our clients.

I'm probably about 50 - 50 for our company.  We get (and encourage) referrals.  I have a strong SEO for our website. It's been out there since 1996, so Google ranks us well for authority.  I find having both works well for us.

I have some retail accounts that are heavier in the advertising area for leads.  Generally, the longer a company has been in business the more easy it is to get referrals.

For most businesses, I find there is a need to get some leads from advertising or marketing.

As for networking --  I personally have never been able to make that work. I know a lot of people that find that useful, I am just not one of them. It has always been a total waste of time for me.  In fifty years, I have only had one person buy from me as a result of a networking event.