Paid ads for a small productized service

I'm launching a productized service around newsletter production. I can afford decent acquisition costs with the business model; however, I'm pretty clueless about running paid ads.

What platforms do people like to run ads on these days for B2B services? How to determine keywords to target for a service in a SaaS-dominated vertical (all the email providers run ads around it)?

Also open to other outside-the-box suggestions!