I think the key factor there is "focusing on creating good content and posting it on steemit frequently".Good content would lead to earning of cool cash on each of your post and at the same time you earn more steem power naturally without forcing it.Buying steem power would be more useful for those who cannot create content and are just looking for content they can upvote and earn curation rewards....or probably the person wants to upvote his or her own content.