Here's how most people start running Ads:
First, you see someone's ad in your feed. You notice the interaction, it's high.
You think back to a time when you saw someone talk about it before and how great their results were.
So you think, huh! I need to run ads. This seems to be a effective! And what do you do? You go to your business page and boost a post for $5.
Unfortunately, you don't see much traction.
So you think WTF! Let me try again.
You boost another one for $20... then another for $50... and before you're know it, you're boosting posts here and there but yet - your list still hasn't grown, your sales are still stagnant, and you haven't seen anything to show for all this money.
Womp womp womp.
Reason why? You're boosting posts!
Boosting a post is the same as telling Facebook, "Hey, I want to run an ad to THIS POST and I'd like to get as much ENGAGEMENT on that post as possible."
Engagement could be anything: someone liking the post, commenting on it, sharing it, clicking on it, expanding to "read more" when there's a lot of text. Anything. And that's what you're telling Facebook you want more of.
But engagement alone WILL NOT give you leads and sales! Many people "engage" with stuff blindly. Many don't even read the post. They just see it, think "cool" and move on. If you're boosting posts you're wasting money!
Don't do it unless you have a SOLID STRATEGY for it!