the best way is to tell people! tell family, friends, coworkers, professors, ect. get the word out and someone will buy something! and you also never know who knows who so even if someone doesnt want to buy something from you they might know a person who will! from there you can begin to build a business and connections.
Create and post things you like and don’t feel pressured to stick with whatever content you start off posting. If you want to reach a certain demographic/group of people maybe include a few pieces of fan art around your other works to draw them in just be sure to mix things up. I’ve seen people get stuck in the fanart cycle and it usually ends with them getting burnt out and growing to hate the fandom they used to grow their account