Where can I buy legit backlinks?

Hi, I am trying to optimise the SEO for a childcare.

Used Ahrefs to increase our health score from 33 to 98. However, our domain rating is 7, referring domains is 30 and backlinks is only 177.

Any suggestions on where I can buy legitimate backlinks? Also, how can I increase my ranking other than improving our blog content and putting the keywords inside the blog?

Thanks!