Which is the best marketing strategy used for eCommerce business?

Pick a product that is already selling , drive highly targeted traffic to your store with good call to actions, try a $5 a day Facebook ad for 3 to 4 days to gain some data, then create a lookalike audience and increase your spending budget and continue to scale up if the results are good.
I like some offline marketing methods a lot! I have been using some promo items like Soft Enamel Pins for it, and they really work! People like such small cute stuff a lot. What do you think about it, guys?