I need to radically improve my BACKLINK profile for UK site

I built ANOTHERGUITAR.co.uk in 2019. For 12 months Google loved it and it did really well. Unfortunately Google cottoned on to the fact that the guitars are all coming from eBay via a scraping plugin. I have now improved the quality of the posts (about 100 guitars added daily) with the help of ChatGPT adding unique content to each post - altering the H1 header and Title so it's not the same as ebay etc.

Here's an example of a new POST > https://anotherguitar.co.uk/guitars-for-sale/second-hand-acoustic-guitars/epiphone-dove-pro-acoustic-guitar-230-00/ the first TWO paragraphs are AI written as is the "More about Epiphone Guitars" paragraph under the bullet points.

Now it's time to radically improve my backlink profile which is pretty crap right now.

Can you help?

I am happy to put £100 at this as a test. If it works I have other similar sites (ChronoDivers.com) that need similar attention. I am interested in quality (niche / relevant websites) over quantity (crappy directories etc).

FYI - I have been involved in SEO (SEO Goggles.co.uk) for 20 years and made a living from affiliate commission on my websites - HOWEVER - I have always struggled with BACKLINK building.

Let me know what you can offer - look forward to hearing from you.

Tristan H