A love of storytelling, and a love of art.
While I built up a readership on Tapastic pretty fast, a big part of that is because I spent a decade posting art on the internet in other places before that - moist of it to crickets chirping in response. It was rare for me to even get 5 notes on a piece of art I posted on Tumblr, because I rarely do fanart (and still don't do it very much).
It can be discouraging, but my love of drawing and my love of telling stories has always outweighed the lack of response to them - and so I kept going, and little by little, I started gaining a regular audience. It takes a long time, but for me, it has been worth it.
Allow yourself time to find new ideas.
Regular updating schedules on webcomics are important if you want to build a readership fast, but readership doesn't mean a thing if you can't do anything. Then it's just a big crowd of people sitting around waiting without anything happening.
So allow yourself the space and time to not draw all the time. Go outside. Read a book. Listen to music you like. And - this is going to sound strange - allow yourself to be bored. Boredom builds creativity, and begins to teach you how to make something out of nothing - being left idle for too long, your brain is very likely to start making stuff up to keep itself entertained.
