As usual, Wildbow gives excellent advice. I will add that it's really, really easy to talk yourself into believing that no one cares, that all of your work is for naught, that you should give up. It's also tempting to self-analyse, to wonder "hmm, maybe if I do this and this and that I'll get more readers." Put both of those the feelings aside and write what you want to write. In the end, the fans you really want are the ones who like reading what you like writing.
Now as far as networking...
I've had very mixed success with r/writing and r/SU&W (although I've never tried r/worldbuilding), but then I've had a tumultuous relationship with Reddit as a whole. I've had more success with the several little mini-communities of serial writers (I actually find them mostly via serial writers on this site)
(I hope none of you mind me sharing links, and sorry if I get any of this wrong)
This is a cadre of superhero-story authors called "The Pen and Cape Society". Its members include many names you might recognize from WFG: Jeffrey Allen (Portal), Drew Hayes (Super Powereds), Palladian (Super), Landon Porter (The Descendants), Christopher Wright (Pay Me, Bug!), Jim Zoetewey (The Legion of Nothing)
Originally started as a place to roleplay games of Brennus, Tieshaunn's chatroom has picked up a large number of serial writers who gather and talk (sometimes) about writing (ironically the roleplaying has now taken a backseat and moved to a different site). At varying times of the day you'll find Tempest (Mage Life), Truth (Raising Angels), Syphax (Stone Burners), Mahasim (Watchmirror), kspam (Goodfae), , and of course Tieshaunn (Brennus)
The Writer's Lair
I'm hesitant to put up a link to this one, since I don't know if it's invite-only or open to all or if they want the link public. This group is pure editing/writing; they post a chapter of their work in a gigantic google doc and then comment on and edit each others' works. Composed solely of WFG serialists: Psycho Gecko (World Domination In Retrospect), Underwhelming Force (Sins of the Fathers), Syphax (Stone Burners), Fallintolife (The Named), Farmerbob1 (Reject Hero/Symbiote), Chrysalis (Anathema)
Technically it's a site for starter serials, and appropriately enough it's just starting out, but since it's dedicated to writing serials, that's pretty much all the forums are about. You can find a few familiar WFG faces there too; I know I've seen SGL(Tales of the Big Bad Wolf), Tempest, and Jeffrey Allen post there once or twice.
I tend to hover silently lurking all over the place, so I don't really count, but I can't tell you how helpful the advice and tips have been that I've gotten just by reading the talented lads and ladies in all those groups!