Ask HN: How do you handle marketing on side projects?

I built a Telegram Bot (@MyScheduleRobot) and waited a couple of months, and then this happened: No one used it. I told the people I knew about it, and then a handful of people used it. I am accepting tips there and my intention is to receive some by providing something useful to people for free. So I have to do something about it.

I'm interested in both: concrete hints on what to do about this and the bigger picture: What is the role of marketing in solo side projects? Do I really have to pay in order to deliver something to people for free? Should I go with the: "If it doesn't grow by itself it should die"-approach? I'm keen on any low level and high level perceptions and opinions on this.