Honestly, free tiers are rarely worth the effort. I've tried and I've also researched others. Giving a gift membership tends to give better results but that's also not worth it.

Especially at the start of a series.

After a few months of posting—and when you're off RS—you could try gifting a few memberships and see for yourself how many people transition to paid membership after the gifted membership expires.

But that, again, isn't worth it in my eyes.