Man, I didn't want to comment until I was done BUT since the game has a stats system but no actual stats screen to keep track of aforementioned element, I need to ask: what is needed and how much of it to defeat (or kill) Rita? I'm currently focused on training with Ferry and giving "essence" to Azula. Already finished everything else, just need to beat Rita now (if it's possible and I hope it is).
I'm sorry but the Rita questline is currently not finished. It will be available in a future update. I don't know when but the script is about 50% complete.
Stats currently do nothing except improve money gained from work. In the future, I'm planning on implement more uses for the stats but right now, they don't do much.