The most inexpensive way to advertise is through digital marketing channels such as social media, email campaigns, and search engine optimization (SEO). Social media platforms like Facebook, Twitter, Instagram and LinkedIn are great for reaching a wide audience quickly. Email campaigns can be used to target specific audiences with personalized messages. SEO involves optimizing your website content so that it appears higher in organic search results. All of these methods are relatively low cost compared to traditional advertising methods such as television or radio ads. Additionally, they provide more detailed analytics which can help you track the success of your campaign and make adjustments accordingly.