Can't provide locations but can give you some types you can look for.
Albion: From Snowdonia -> Ellyll Guards or Cyraeth, they are on the way to pennine, Cyraeth on west side of lake and Ellylls on east side From Sauvage -> Closest useful pet is the Isolationist armsman/wizard on the hill when entering Pennine, no good pets in Sauvage afaik (you don't want a big ass tree cuz people will see you from miles away).
Midgard: Start with taking an Aurora (blue orb thingie) and then switch it up to a Cocatrice when you can (pet with stun that causes no immunity).
Hibernia: Either Granny/Fachan/Grogan, doesn't really matter since they are all relatively equal. You used to take a Goborchend piercer on Uthgard for the dot that interrupts but I think they have been nerfed/removed. If you are running solo you could pick up an Empyrean Elder once you get to Breifine/Mount Collory but they're kinda meh on this server with all the buff pots and charges available.
P.S. Don't be the guy who puts his pet on defensive letting it live its' own life, seen so many idiots letting their pets run wild, either hitting the tanks or breaking mezzes. Put it on passive and force yourself to learn to manage it, once you do it's super useful. Last but not least, BIND YOUR PET CONTROLS, mouse clicking is never ever ever ever more efficient, watching clips with people clicking everything makes me cringe.