Building PBN for your SEO is good, but PBN's are

 quite expensive if you want the best outcome.

If you want cheaper and yet best solution go for high PA/DA expired Tumblr's, and get the same benefit of having PBN.

As you already know Tumblr is the most popular Web 2.0 and most trustworthy domains with a MOZ DA 99.

PA does matter in SEO World whether its a Blackhat, Grayhat or white hat. In this gig i will give you 15 expired tumblr blogs with PA 28+.

This will boost your ranking in matter of weeks,  you can add this to your existing tumblr or create a new account with these domains. Also this is good for your link diversity. :)

GIVE IT A TRY, ITS SUPER CHEAP