Social media is all about engagement and discovering your audience. I'd always recommend against buying followers as this doesn't help you actually discover your audience and skews your social media analytics.

The other reason you need to be as truthful about your audience as possible is for advertising. Ads on social are quite effective if you narrowly target user segments. I feel as if their ROI is far better than search ads/Google Adwords (unless you were re-marketing people with your Adwords).

The true power of social media comes from spreading a message (virality) and gaining thought leadership. It is in building a following and having advocates. This simply takes time. There is no short cut. Automation can come off like spam and hurt you.

More than happy to chat further if you like. I do a lot of social media campaigns and analytics (though admittedly more for big brands who may have bigger budgets).