unfortunately Google seems to have a minimum bit for ads to show up (even if G. will not admit it). And if you want your ad to be placed above SERPS on the left this will be $ 0.40 max. CPC or more. Try with a relatively high bid and than slowly try to minimize it.
Are you sure I have to work on CTR even with no competitors? I thought to put the price of my product inside the ad to receive only interested customers. If my CTR is not good Google can choose to put nothing or me. What is better for Google? 0 or some $$? There is nobody else so why focusing on CTR? I only need people interested in purchasing my product.
Why should Google show your ads for free? If you create an ad that converts well, you should be ready to pay a price for it. As long as the ad shows up often enough number of conversions is more important than CTR.
What's best for Google is to show ads that people like.
"As long as the ad shows up often enough number of conversions is more important than CTR." True, but that doesn't mean CTR is unimportant.
"Are you sure I have to work on CTR even with no competitors?" Yes, quite sure. The higher your CTR, the lower your CPC, the more ad imp share you'll get. Definitely work on Conversion Rate too (or even more than CTR), but if you do a sloppy job on your CTR, your lack of competitors won't give you a pass (it used to, we refer to that as "the good 'ol days"). Google will continue to ask themselves, "do people like this ad?". And they primarily measure the answer to that question using CTR.
They don't care about taking any one advertisers money, they care about the consumer's experience - a superior approach, it guarantees advertisers will line up to pay, because this is where the traffic is. Please the searcher / shopper, and G favors you. It is that simple.
your lack of competitors won't give you a pass (it used to, we refer to that as "the good 'ol days").
As often: It depends. If your keywords get a quality score of 5 or better, CTR is less important. It becomes highly important when it goes to 3 or less. The difference between 6 and 8 has less impact on the CPC than the difference between 3 and 5.
You'll probably find that Google is not running ads because of prior poor performance from everyone who has tried ads on the term. In that situation you may well need to bid high to get on the page but it is possibly also not going to be a very lucrative keyword. Often this is the case for broad keywords where their isn't much to latch onto, e.g. lots of geographic location terms.