Nice question well i have not launched any website but my friend has launched site and i was there in his marketing site as we use to market our site by google and youtube adds which shows in browsing the net. 

Yes it is beneficial for maketing our site as we can get more customers in short period of time and can get a massive audience by promoting our site from very major source of marketing. 

Social media is the best way for marketing todays world as there are more than billion of people using internet daily and today i think there will be very beneficial to get the mass of audience in our site for prompting our site in social medial platform like Facebook, Instagram, google, Mail marketing, youtube is also a good source to promote our videos in front of browser as this is the best ways i prefer to promote my site for getting majority of audience to my website.