I would recomend buying Rasputina (because she is a Master) and then, buy Kaeris and add her as Henchman so you can play them both at the same time.
If you buy only Kaeris, you will have very limited range of models (not bad but limited) but with Rasputina, you can have everything from Arcanists (even Kaeries) and in my opinion, Kaeris is better as henchman than as a master (with option of totem)