If there's any focus servant you REALLY want, then save up for them. If your team feels like it's lacking, then keep in mind also that there are free servants from events coming up. Gudaguda gives Nobunaga and that should be coming out pretty soon. Honestly though, Elizabeth and Kintoki should do you good for a while. I'd only ever suggest rolling on a banner with something you don't want if your team isn't cutting it. Also remember that if you think you might get something good off a yolo pull, you won't. Always think this way, or if you want to pull, go do a pull simulator or something. If you're looking for upcoming servants you might want to get, here's an image containing all the banners released in Japan in chronological order. http://i.imgur.com/Nlf8lyj.jpg Edit: Also, Stheno is the worst Assassin in the game. You have my condolences.