Looking for AdOps Consultant / Agencies for Direct and Programmatic Selling

We have a website of social network/clean user-generated-content/video content with 1 million MAU/10 million Page Impressions per month with traffic in tier 1 countries and mostly on mobile devices with no advertising in place. We have lots of highly engaged users in all age groups and we have interesting first party data such as gender, age, interests, etc. that could be valuable.

We want to start monetization for display, video programmatic ads, as well as sponsored videos and direct sales. How do we get started? Should we work with an agency? Or work with someone who has a list of contacts in the industry so it is easy for direct sales? Should we try to find a consultant?

Looking for recommendations on how to approach this and get started. Thanks for any tips that will help us get direct deals at high CPMs based on our first party data!