Hey there. I'm Tim from The Next Step, a digital AdOps agency with teams in Brisbane and Vienna. We focus on pretty much exactly what you're asking for. Sell-side ad stack optimisation, CPM increase and first-party ad sales. We also throw in a bit of ML and artificiL decision making, to increase the efficiency of the implemented product. We'd be happy to do this for you, and help your site reach more people, and make impressions truly count.
If you'd like, you can send me your site's URL and I can make a basic analysis, as well as point you towards a few resources that may work, and if you decide you would like to work with us, we can build on that existing proposal.