This is going to be a bit of a compare and contrast piece, covering two now well established series, another that is in a fledgling state, and two others that I have great hopes for. The established series are Galaxy's Edge from Nick Cole and Jason Anspach, and the 4HU(Four Horsemen Universe) headed by Mark Wandrey and Chris Kennedy.
Galaxy's Edge does a lot of stuff very much right. They started with a bang, filling a desire with their #starwarsnotstarwars postings on twitter, and marketing that as the overall idea of the series. The money they spend on covers is large, but clearly successful, as they get emails from new readers drawn in by the covers. They've even been spotted in a few physical bookstores, something few indie books get, at least before they get signed by a publisher. Their output is about a book a month, and while that's great, all the books are by them, and start feeling the same after so many.
4HU started off a bit slower, with the first four novels being by Wandrey and Kennedy at 2 books each. And then they opened up the floodgates to other authors with anthologies. This let them get a feel for the audience early on and built the draw and talent pool available quickly. Currently, it sits at a 3 week release schedule plus some. The cover art varies a bit more, but there are only a couple I would actually replace of my choice. The cycling of other authors into the release schedule, with the novels tying together, but not directly interfering(through edicts such as only Chris and Mark actually write the 4H, and even appearances of characters from such need approval) with the other stories.
Silver Empire recently had a successful Kickstarter campaign for a universe called Heroes Unleashed, with interesting ideas that are somewhere between the two. What was termed Wave I will have 5 authors doing novels(likely series if successful). Morgon Newquist(school of arts and war) created this world with short stories in two anthologies(Paragons and HA! HA! HA!), and the others involved include some others I've reviewed here: JD Cowan(Grey Cat Blues, Knights of the End), Kai Wai Cheah(No Gods Only Daimons, Hammer of the Witches), Jon Mollison(Sudden Rescue, Adventure Constant), and Richard W. Watts, with whom I am unfamiliar.
Bradford C. Walker and Brian Niemeier both have run Indiegogo campaigns(Brian's is still live), related to their #AGundamForUS work, and both have some good ideas. Now, if both do well, they will eventually face the challenge of putting out new material and keeping a fresh feel to their stories, which is where I think Galaxy's Edge has begun to fall flat, so this is no mean feat. My advice would be to do a contained series, maybe 6 books, at first, and perhaps invite other authors after, either for shorter arcs or standalone novels. Yeah, this is a throwback to the books they are somewhat imitating, but it did work then, and should work again, if they find authors that get what they're doing.
When you play Social Justice, the world loses.