Just a quick word on this. FFnet is full of one-shots (that is, stories with only one chapter, usually a fairly short chapter at that) and that's cool. It's also full of longer stories, with new chapters posted every once in awhile, which is also cool. It's even more full of longer stories that are abandoned in progress, and that's not cool, man.

If you're doing a chapter story, your readers expect to find out how it ends eventually. It really sucks to be enjoying a story and have it and its author disappear off the face of the internet. Don't do that, I beg of you. I highly recommend finishing at least a rough draft of your fifty-chapter masterpiece before even posting chapter one, but I realize that's not realistic.

After all, everyone wants fast feedback when you start writing something massive, even me. So I implore you, once again, to outline. It'll help keep you on track, it really will.

As for that fifty chapter masterpiece... Are you sure you can handle it? You are? Okay, then. You're not? Why don't you start with a one-shot, or a five chapter masterpiece instead? It'll help you get a handle on how to plot and how to write dialogue and find your character and your tone. If it works, then more power to you, go ahead with the fifty chapters. You're prepared for it.