The purpose of a CTA (Call to Action) as the name suggests is to generate a response from the prospect to the email (usually a yes). It should be clear and concise. Make sure you’re not asking for too much, keep it as low friction as possible for the prospect. Take permission before sharing anything.
Understand that the prospect might not be super willing to respond to a random email from a random dude. You’d want to build enough credibility through your rest of the body to really make any CTA work. A good CTA is an extension to a good offer.