Depends on the topic of that site.
Normally we show the existence of your business through marketing/social media and then make those visitors come back again through the quality of our content/service.
If we provide high quality content/service, then we see visitors/clients graph going up day by day. Whereas if we do huge marketing but the quality of our content/service is low, then the graph of our visitors/clients won't stay steady, and it keeps going up and down and then permanently down after sometime.
So, we can say that field related knowledge/skills, on-page and off-page working, all these are important for the success of online business.