Finding agencies that offer Blogger Outreach service is difficult these days 
Most of them are actually selling PBN posts. Well, I won't be able to suggest what exact link building strategies you need to start with.
But, I could try suggesting you some digital firms based upon my experience.
I have tried Fatjoe.com and submitcore.com, both provided me with excellent placements. However, the problem here would be budget. Fatjoe is pretty expensive. Submitcore in comparison offered equivalent quality at cheaper price. Try contacting them both and see which one suits you better! Good Luck 
