Here's the link to the section you needed in the training portal: https://dovetailmktg.kartra.com/portal/mgsitlogin/subcategory/158
One of the easiest things you can do to reduce costs of leads and get better leads is to engage with your own post and the comments others leave on your post.
Engagement (i.e. comments) on an ad indicates to Facebook that 'people like the ad' so they start showing it for less money. On top of that, intelligent and informative replies to comments helps answer questions that people may already be thinking and it's not uncommon to get leads off the post commenters because you can ALSO message them directly, which I recommend.