Before talking about SEO, you need influencers to bring the first visitors to your websites because no search engine is not going to recommend a new site unless it is loaded with high traffic. And also the content needs to stand out, if it is just similar to the other websites doing then you will be shown in the down order or after few pages.
An advertisement through social media can land him real visitors as long as the content is good or the ad that he has made is interesting. If it's not interesting and then he's still doing some ad/sponsorship like in Facebook, that won't bring him much engagement and traffic to his website.
With the combination of all the ideas that he has on this thread, he can test and have his own experiment but as per ads, it requires some budget.