It's tricky to promote yourself. All I can say is hit up every place possible and be dogged about what you're doing. Post a link of your comic everywhere you can while at the same time reading and perusing others.
Also, leaving comments with people who are also trying to do web comics and showing support for whomever isn't already famous is a good way of gaining new friends in the field and hopefully loyal readers too. Share to all your friends even though they might start to roll their eyes at you eventually and never hesitate to tweet, share, or whatever you can every time you make a new comic page.
Basically, keep banging on the door wherever you can publish it, eventually something will start building. Keep the momentum going once you do.
Two places I recommend to start is:
Also, I'll check your comic. I love meeting other people who are trying to do the same thing.