It kinda depends on what type of pets are there. Im usually trying to get pets that could be higher level then my character. There are poisonous, ranged, healing (if you have the premium edition), stunning, freezing. It just depends on what kind of a monster youre better with. I suggest getting ones that are higner level then you. Thats kinda it.
Hmm... well i think the revenants or however they are called. Or if you arent in the golden age peaks, but somewhere closer to the beginning like in the eastern shore you can find those poison beetles that shoot poison in a ranged attack. Umm if you are further then golden age peaks... well there wont be anymore poison monsters higher then your level. Its best if you tell me whats your level and how far are you.