Well, it depends. If you are getting enough organic traffic naturally then you might not need to. However if you are struggling with your website's sales and traffic then consider going for paid advertising.  Because according to Google, using Google Ads can result in an impressive 800% return on investment (ROI). And you already know about google shopping and PPC campaigns. So if you do not get enough traffic, consider going for paid advertising. But always remember to do it in the most effective way.