Organically is the best way.
I have gotten to know my readers, I am invested in them and they are invested in me. Readers are giving your story a chance to be read. They are giving you their time and I treat them with the importance they deserve.
There are millions of free stories on Wattpad that they can read, but they have chosen yours. If you remember how special that is then you will grow your readership because you have respect for the ones that are giving you a chance.
I reply back to my comments as much as I can. I don’t go off on someone who doesn’t like the story. That’s their right as a reader not to like something. Just be yourself and people love that. Readers are making a connection with what you write and you have an opportunity to make a connection with them. It’s an amazing process and good luck.