To break it into the broadest possible categories: Riza could go for more character development type stuff, or go for plot development type stuff. There's overlap between both categories, but it does change the balance of which one us initially takes the lead in setting things up.

There's no strict 1:1 plot:player mapping, so don't worry about crossing paths with other players (or other players getting interested and crossing paths with Riza).

[edit: and having the plot stuff driven behind the scenes by player choices is working out fine, so far, too. Running off and Doing Your Own Thing still serves the grand design in mysterious ways ]