Creating a solo game adventure is actually extremely easy with Zombienomicon Eisegesis.
First, metacode it out, either longhand writing on paper or on screen in notepad.
Work out all the alternatives for the main thread of your story. Remember that to really involve other people, at key points in your adventure story you should enable the “Extend” option so you can have other people enhance and alter your game.
The flow should be logical no matter whether your story is arbitrary and silly or deathly serious high fantasy or a spy story or something.
In terms of making people use randomness, there are several options. I am coding dice rollers and so on for a future release but for now, it open to you to tell a reader to roll a dice or flip a coin and then provide the options. What I am currently doing is writing out charts of outcomes, say 6 different wandering monsters on a wandering monster chart. Then instead of a roll of 6 always being the worst monster I randomize myself which position will be which monster. Then in an Episode, I add a paragraph saying for example “Pick a number between 1 and 6.” Each option leading from it is one of the random monster encounters.
USE THE POWER of the Extend-A-Story system! It is superior to physical gamebooks in that it can link back to a previous paraagraph. So for example you can have a huge long winded explanation, description or battle, and at the end of even 100 Episodes simply link back to the original adventure chapter. Likewise a long conversation with a character can return the reader to the original Episode. If you also allow extensions that will make your adventure literally, and rapidly, infinite. There are examples of this already on the site.