We use SEO tools and craft a keyword strategy. Then we calculate the total amount of monthly leads/sales and cost-per-lead/sale using the formula on this post.
If you are using Google Analytics to count conversions from Google Ads, you may be missing a large chunk of conversion data.
Start new campaigns with a manual bidding strategy until the algorithm has enough data to switch to automatic. Then, see how high you can push the algorithm to automatically raise its goal (i.e. target CPC of $X could be the goal). You must have conversion tracking set up correctly before running any campaigns or else you will be feeding the wrong data into the machine learning algorithms, which will obstruct its ability to get results. You can check this by going to the Conversions report and checking the “Include in Conversions?” column and making sure that only the appropriate conversion actions are included.