Currently, I lock all of them. I do this because I already have an e-mail list and large following on Medium. You can do either or. You can also mix it up. Shannon Ashley went ‘all-in’ on Medium’s Partner program and built up an income from scratch. Niklas Göke also went all in on MPP, but like me, he had an established audience prior to switching to locked posts only.
Going all in can lead to a good income. The only caveat, if the program gets shut down or Medium goes bust (neither of which I see happening anytime soon) you’d have to start at square one.
To hedge against that, you can get traffic to your Wordpress blog and build your e-mail list through SEO, guest posting, promoting your Wordpress site to your e-mail list, etc.
Hope that helps. Just start!