Depends what you want out of the pet, you havn't got enough for an omega killer and tbh the 2nd best afk place is mags. A popular option these days would be a pet with around 35k power, if I remember correctly there's one for sale for around 1.5b. With that price you got lots of tickets left for other things aswell,
*edit* Gonna let you know that I have a mag killer. Only 23k power but good enough, in my opinion anyways. Hit me up in game if you wanna talk
IGN: ToxicZone