Just a warning; if you get frustrated/hate regular pvp, pet pvp can be just as infuriating, though far less dependent on twitch
That being said, starting out pet battling in pvp is rough. When I started, I think I had like 15 lvl 25's, and a weird mix at that. I didn't have an understanding of what some of the more popular pets use that I didn't have, and had to learn through a lot of trial-and-error. When I first started, I probably lost 3-5 matches for every match that I won. But then I began to understand synergy a bit, and began building up a stable of useful pets and experimenting with different setups. Also, I knew nothing about breeds at first, which led to some sub-optimal performers. I do not advocate tons of addons, but a Pet Breed ID I would consider a must-have. Knowing the breeds that have/want can save you SOOOO much time collecting and leveling the pet you want, and not having to go back later to get the breed that you actually want.
I think my most successful starting team was Son of Animus/Yellow-Bellied Bullfrog/Magical Crawdad. I was lucky and already had leveled the P/P breed of frog. The SoA is pretty strong vs. just about anything, the frog is great against undead (racial and Lick) and elementals (Frog Kiss), and the crawdad speaks for itself. While I don't use this team anymore, it helped me a lot getting started. For a new pet pvp'er, I would recommend getting a good flyer such as a moth, a good aquatic such as a crab (a P/P Emperor Crab is easily captured and a very strong pet), and a strong undead. The reasons being that the moth will help with speed comps (flyer racial gives big speed boost when they are over half health), the aquatic is strong against undead dmg (you will see TONS of Unborn Valkyr's in the queue) and crabs have offensive and defensive spells, as well as a heal, and Undead are strong against humanoids and have the free "rez round", which to me is the strongest racial.
Whatever pets that you decide to use, prepare for a steep learning-curve, but ultimately a very pleasing diversion to the monotony of WoW. At this point, I enjoy pet battling far more than any other activity in this game. Enjoy!