Buy first, spread later.
Buying the book is only half the fun. The other half is when you read it, and enjoy it so much you tell others about it.
Authors first want the first half. But what they really want is the second half. Craft the right story and the second half makes the first half automatic. And it increases it too. But the first half needs to work a first time for it to be a thing at all. That’s why both are important.