You have a courteous le if options. I use formloom, which can store the emails on a google sheet or SQL database and redirects on completion. I believe Greg Barchards Forms Plus and Joe Workman’s Post Office stack can do the same.
Services like MailChimp etc have code for their own form, which you can simply paste into an html stack.
I now have an email service for this. You can start collecting emails for only $1. When you’re ready to send, you can upgrade to a paid plan. The email plans also have a discount for Chillidog users too (just open a support ticket)!
For a CTA, I’m working on a Stack that will allow you to integrate with my newsletter. Joe’s PostOffice Stack should already do this and FormsPlus will in the future