The products listed on your website are supposedly meant for a niche category of audiences which is why ROI cannot be predicted by anyone. Infact the predictions given by google forecast interface or facebook forecast can also prove to be wrong. For such kind of products, it depends how well you describe your product through your creatives and ad copies. I suggest you should doing it manually starting slow and raising your daily budget gradually based on performance of keywords. You must also pay more attention towards negative keywords, audience targeting, demographics, and bidding strategy. For more info you may connect with us: info@onezeroin. com