PNB(A Private Blog Network ) is the really effective technique to rank your website because a strong backlink profile is one of the most important ranking factors.
The links from PBNs will send a lot of link juice to your money site and you will see the increasing if your SERPs positions soon after you build this new links.
You can buy links from the PBN of other people but you can also build your own network. The last will be more cost efficient and secure for you.