Evernote is also quite easy to use, especially if you have different documents (world building, characters, plot, backstory, actual story, etc.) and want to keep them together. It uses 'notebooks' which can then keep those different documents in the same place. It is also free and works on-line (in-browser, app, mac/pc-software and synced between devices) and offline as well.
I've switched from Google Docs to Evernote because Google Docs has no offline function (on Mac/Pc) and because I have a lot of different documents like mentioned above. Furthermore, and I may particularly picky here, the actual software runs smoothly, which means a lot to me for some reason.
It does however NOT help you with a logical format like Scrivener does, but it is a good place to start since it is free and keeps things manageable.
Remember that There are no rules, in creative writing. There are guidelines and expectations for different genres, but you don't HAVE to follow all of them or fulfill exact criteria for your work to be accepted. Some genres may be less forgiving than others, but if you want to write about X in some way, do it that way. Don't force an unnatural style or language into your work. It will not be authentic, and authenticity is more important than fancy language. You can't please everyone, but if you find something interesting, others will too.
Warning, personal (in)experience incoming:
Now, I'm aware this might make me unpopular among some of the more experienced reader/writers here:
I don't believe you HAVE to read a lot to be able to write.
Let me explain.
I am in no way saying that you shouldn't read or that it doesn't help improve your understanding of language use, genres, structure, vocabulary and so on. By all means, if you read and enjoy it, do it! I am however saying that you can capture a reader without having read a lot yourself, if your writing style is interesting and if your story is captivating.
This is my own situation: As a kid, I had trouble reading for more than 5 minutes without almost falling asleep, and as a result I never developed a habit of reading. I also read quite slowly today. I have read probably a small percentage compared to most of the people on this site, but that doesn't stop me from creating a world that people find fascinating, and so far I've received (surprisingly) good feedback for my writing. I don't mean to come off as arrogant and disrespectful to the world of writing or the people on this site, and I'm not saying that I am or will ever be a great writer, but then again I am not motivated by the thought of becoming a world-wide best-seller. Sure, that would be fantastic, but I write what I write because I've thought, brainstormed, discussed, dreamed and felt passionate about this project to a point where I simply can't NOT do it now.
Yes, I feel unsure about many areas of my project that I may have been less unsure of had I read more, but passion kills experience most days.
Main point of this: There's no reason to postpone your own work until you've read x amount of books. If your passion is there, go with it.
Also, this site and its users are awesome.
Best of luck with your writing!