The easiest way it's creating a custom audience with whoever visited your post-conversion pages.
When you retarget them, offer them something they haven't bought before.
According to Adobe, who already bought from your shop, is more likely to spend 5x more than a first shopper.
Moreover, 41% of overall revenue for eCommerce sites in the US are from repeat shoppers.
Are you missing out on this opportunity to increase your e-commerce's sales? :-)