Most visitors leave without buying — not because they hate you, but because life interrupted. Retargeting shows ads only to people who already met your brand, which is why it's the cheapest conversion in advertising.
Install Meta Pixel / Google tag. Build audiences: all visitors (30d), product viewers, cart abandoners, past buyers. Each gets a different message.
Cap frequency, exclude recent purchasers from purchase ads, refresh creatives — being followed by the same banner for a month damages the brand.
Bottom line: retargeting turns 'almost' into 'ordered'. Set the pixel today; the audience builds itself.