Launching a B2B agency - Need Advice

Guys, I'm looking to start a B2B marketing agency, focused on

  1. Product Marketing (Clear positioning and messaging)
  2. Account Based Marketing
  3. Content Strategy, Content-Driven Demand Gen

I have experience in Content and Cold Outbound lead gen, but not (1) and (2). Have playbooks for all areas, but not experience.

Should I just focus on (3) since I have the experience or "learn by doing" and sell all three services regardless?

Pls give constructive advice guys. Thx.