When you decides make your online presence, you should create either a website or blog. Its should be a destination where you wanna bring your audience to. If you are into small business and you have limited budget for digital marketing, then your best choice should be blog. Its free to create and templates makes it user friendly.
It could save you the design costs up to a level. And you can keep it active with posts. That will help you with SEO as well. You should have noticed, most of the big companies use blogs to keep the interaction with their customers. Eventhough they have websites, blogs helps them to know customer feedbacks in realtime.
All the other social networks and advertisements should redirect your customers to your blog. And they should be given space to share their views on you and your products. You can start by exploring wordpress.com, blogger.com to make your online presence.
All the best guys.