I use Scrivener, but I guess I'm not very scientific because I just use it so I can have all my projects available on one screen when I want them
For a fantasy story like you're talking about, you might want to start with an outline. Beginning, middle, end. Then fill in the details, easy peasy
Don't worry about length or even if you're going to have it as a series yet. Right now just focus on what you're going to want to have happen. What are the overriding points you want to express in your story: love, friendship, revenge, etc. What is the base message of your story? Why would this group of people want to hang together?
Sometimes my outlines are very sparse--just a few scenes strung together that I happen to want in a story--and then I let the characters carry the day. I give them a goal to reach and I have a few set events that take place in their world, but otherwise their personalities decide what they're going to do and how they're going to react to any given situation. Other times I sketch out every single scene, keeping in mind the rules of "And and But."
"Tony Stark is enjoying his life as a billionaire playboy weapons manufacturer
and enjoys showing off
and is very proud of his new weapons system
and is in Afghanistan showing it off,
but his convoy is attacked
and he is wounded with his own weapons
and taken captive which leads to him planning his escape. He builds the first armor to save himself and Yinsen
and they stage their escape,
but Yinsen is killed
and Tony is filled with regret and remorse for what's been done with the weapons he's built. He returns to civilization
and builds new armor
and becomes Iron Man to make up for his past,
but his old armor is found and reverse engineered to be used against him."
Every event that happens in your world should make something else happen. It keeps your characters motivated and the story will flow forward naturally.
Also, with dialogue, I was told that "said" is always the best (I'm saying that as someone that edited a story where the author thought '"Don't do that," he ejaculated loudly' was not terrible at all. It was
terrible.) "He said," "She said," "Bob said," "Mary said." The dialogue should flow naturally and you don't need to add a bunch of fidgety stuff in-between; your dialogue should be able to work by itself and the reader will infer the emotions.
Write the story you want to read. If you get bogged down somewhere, put some placeholder text describing what you think should be there, and just keep on going. You can go back later and fill in what you missed.
tl;dr Hope that helps
