There are a lot of marketing techniques that are time taking and need an investment for the proper marketing. But Email marketing is one of the best way to advertise yourself with the people who are really in need to buy your product or services.
https://bitarticles.com/education-and-learning-articles/relation-of-lead-generation-email-marketing-and-sales/
http://www.theb2bleads.com/3-best-free-email-marketing-tools-in-2020/
http://www.theb2bleads.com/