My GoogleAd campaign has ended. Exactly 44 people clicked on one of the Ads and 15 signed up in the end. I don't have the final number yet on how many bought a subscription because of the 30-day trial delay. I assume it will be less than 5.
What I definitely recommend is to link Google Ads with Google Analytics and report back when people buy a subscription. This will give an exact dollar amount on how successful the campaign is. I didn't do it because I was frankly too lazy to set up all this for my free voucher. If I ever decide to buy Google Ads for money then this is an absolute must, otherwise, it will be difficult to control and measure the spending.
Another thing I noticed is that despite 5-10% click-through rate (CTR) Google will penalize the ad when not enough people search for a keyword. I can only assume this is to force advertisers to choose more common keywords and increase spending.