I'm looking to have a character that looks for exotic animals to capture and train as pets and combat. Smaller creatures to be on body at all times and can do tasks. Bigger one to ride and have actually attack in battles. Thanks for all advice.
This isn't really covered by the rules, so this is a mix of GM discretion and house rules, but if they're cool with it...
You can rear up to three creatures of the same type at a time with the 'rear a wild animal' use of survival. This takes months to years based on GM discretion. You can also improve the animal's attitude as with diplomacy with the 'handle animal' use. What a friendly or helpful animal does is mostly up to the GM. Giving a single animal a command is probably a move action.
There is also the blurb about treating a legacy animal companion as very similar to a mechanic's drone.
So, with that said. I would say your options would be either to update a legacy class so you have an animal companion to ride, or reskin the mechanic to be a 'biotechnician' with a biological drone.
Having and training the little guys would be purely GM discretion, and honestly, I'd be worried about grenades if you wanted them to follow you around at all times. They'd be in the blast radius too.
I think if I were to house rule this with a minimum of headache, I'd basically reskin the animate dead spell to some sort of bond-animal ritual.
There is also a feat in Alien Archive 2 for having a small, trained pet that will do things for you. Not much else, in the way of published mechanics.
Yeah, get yourself a squox from the Alien Archive 2 to start with.