Keyword research high or low competition?

[Booboo]

I have been searching for this answer and all the results come up with people who want to buy ads in adwords that point back to their site.

I just want to make a microniche site with good content and SEO and place adsense on it and wait for people to click. That part is easy for me.

The thing I am confused about is keyword research.

I understand that if I wanted to spend money in adwords to have ads that point back to my site it would be best to choose low competition exact match phrases/keywords to save myself the money. Understood.

But I don't want to do that. I don't plan on paying for anything other than the domain and hosting.

Is high or low competition keywords best when trying to only rank in the serps?

Should I search for keywords with low pr sites in the serps top 10 because they are easier to compete with in the serps?