This step makes the most sense and is more process-oriented. Join as an intern and learn the ropes.
Joining an SEO agency and learning the ropes will help you learn faster since you’ll be bang in the middle of all the action (and possibly since you’ll have your senior monitoring you). This is a way to learn SEO for beginners, from the pros.
You’ll be more hands-on with the daily affairs, doing page optimization, link building, keyword research, performance analysis, reporting and much more. It’ll also help you set a perspective since doing all that will give a clear set of distinction between your strengths and weaknesses.
Joining an SEO agency gives you an edge since you will also be learning the business aspect of SEO. Lead generation, client pitches, providing good service and ensuring customer satisfaction, and client retention can be learnt from an agency. It could also help you start your agency once you gain expertise on what you are good at.