How much do you spend on one campaign if there's no sale?

I just set up the Google search and display campaigns for SAS program. They are both in initial learning stage, I am wondering at what point if I don’t make sale should I turn off the campaign? After the initial learning stage( i think it takes 7 days for google to learn)?

And also I already set up conversion pixels, but when I tried to optimize for conversion instead of clicks for the search campaign, it shows I will get 0 click and 0 conversion with the daily budget of $20 and the guru list as keywords. If I switched to optimize on clicks, it shows I will get 72 clicks daily. so if I want to optimize for conversion later, I will just ignore the 0 click and 0 conversion google ads showed me?