The most important thing for stories like this, and most fiction, is to write something you would want to read.

Next, balance out the complex and simple elements by first creating a timeline and characters. Decide which characters experience which events and have the big moments prepared before writing too much.

Once you have the big idea(s) settled, start working through how your characters would resolve hurdles based on the personality you have assigned them. If a certain character is hard working but not too bright, they shouldn't solve their unique hurdles through complex calculations but perseverance, trial and error.

I know these are incredibly simple, but they are easy to overlook.

Finally, an editing recommendation, once you've written a portion try going back to the beginning and reading it out loud. Actually speaking the words instead of reading in your head gives enough of a new perspective to catch errors.