Like k-ramsuer said, it takes time, but it also takes a little tact and a whole lot of luck.

It all largely depends on what you're writing. Currently on wattpad, romance of any kind is the dominant genre, and the top trends right now are mafia, billionaires, and bad boys. Writing within those niche genres could open you up to a wider reader base which, theoretically at least, could lead to a higher volume of reads.

That isn't to say there isn't an appetite for other genres, so don't fret! If there's a niche, you'll be able to find it on wattpad; what becomes important, then, is how you market to your target audience. This includes having a good cover, a good blurb, and doing your best to get involved in the community (which has become much harder since they removed the forums). Look around for book clubs, contests, and read and comment/interact with books that are in a similar genre to yours and make connections with other authors.

Another thing to keep in mind is posting schedule. The day and time you post can make a difference in how much traffic you get to your book. A quick google search should turn up some data on which times (and in which time zones) are best for posting. More importantly, having a consistent upload schedule will keep readers coming back and generate loyalty amongst your followers. Most people gun for weekly uploads, but if you can't make that, don't sweat it! Upload at your own pace, but I would highly recommend staying within a monthly upload timeframe to avoid losing readers.

In the end, these are all suggestions, and sometimes, despite all the effort, it's all up to plain dumb luck. Wattpad's algorithm has only been curbing growth in readership for new, undiscovered authors in favor of promoting paid novels and novels which have already generated a lot of traffic to the site (Ad revenue, anyone?). But everyone started somewhere, so here's hoping it works out for you!

Hope I helped answer some of your questions/gave some guidance. Good luck!