In terms of what Wizard said about your plot still needing to have war in rp-present time, I personally have to disagree. To be fair, I'm pretty biased because I never was able to get into war/faction plots for some reason, but I really do think that they've been done too much and, more often than not, done poorly.

Rather, because the plot of your rp is about individual greed re: the stone, I think you could emphasize that members build characters with some kind of wish or "lack" already hinted it or fully explained in their apps. This can be anything from "Character A wants to be the richest person alive" to "wants world peace" to "wants to remain happy." Then provide the option to let characters group themselves together if they want, but on a 100% volunteer basis. In other words, someone makes a knight and decides to be part of the castle guard or some such. Another person makes a thief that's part of some underground smuggling ring. Etc.

I'm also assuming that throughout your rp, the stone makes its reappearance in some way? I would imagine through site events where its existence is hinted at in increasing depth until the truth behind the myth is blown out into the open. That, or something similar, would provide enough forward plot momentum.