You are getting a great deal. You should be using bots to promote your content and not for ROI. If you end up with a positive ROI that's a great bonus.

Other platforms such as Facebook or YouTube simply take your money and offer no money returns but just promotion. Steem bots give you an upvote as well as the promotion. Even if the ROI turns out to be negative, it is still far better than what other platforms are offering.

My advice is, make the best posts you can and then promote but in moderation. Over time you will build a solid following and your content will naturally improve with practice.