how to improve positiong on Google (business with very low competition)

trying to improve my positioning on google. All pages are built under the SEO guide, so basically good.

I have to be the first result for every artist name (NAME SURNAME research on google).
for most of them I am in the first page, because there's a low competition, especially for minor artists.

tried to buy some backlink, but it did not improve so much

post on gmb daily with keywords on post section

also add your gmb on local directory

Don't obsess too much with individual ranks and keep creating content consistently and reviewing which keywords are partially ranking for what you already have to boost them within your content.
Also specialize yourself on better linking. Is a very hard job. Is not a matter of just "buying a couple backlinks". Backlinking is a huge mastery in SEO.