Can I find affordable workflow apps for creating email series?

[yetanotheruser]

Are there any free/cheap workflow apps that would let me create a drip email series using Shopify Email?  The few I've tried will only let me send a basic email...not one created in Shopify Email.  I'm trying to avoid paying $30+ a month for another marketing tool.  I could use Shopify Flow but I think would require me to upgrade to a more advanced version of Shopify than the standard one I'm using.