If you were to actually make a good roleplay server, ie rules to determine how players roleplay, such as in turns with fights done in real time or something of the sort, rewarding players who contribute to the roleplay of the server, and generally putting in effort into it, then I’d have to say do that. If not, writing a fanfiction to gain experience in writing, something you say you don’t have much of, would probably be the best use of that idea.