Hiya
If you have been like me and not gone all crazy and already levelled 10 battle pets to level 25 due to the amount of time it takes to manually level them, then this small trick is for you. This may be quite common sense and already known, but I couldnt find any hints on this iin my searches.
In short, this is a guide how to get one or two lvl 25 pets (when you don't have any) to use as boosters for the pets you want to use.
What I realized when ripping my hair out over how long it took to level a pet trio for the first time, was that the fastest way to gain levels to reach a few lvl 25 pets in your stable to use for regular boosting is to do what I call "catch levelling".
The method is simple. Just follow this small mini-guide.
1. Start off with 3 pets.
2. Browse the map for a zone with pets 1-2 levels above your highest level pet.
3. Go there, find a pet of the quality you feel is enough and catch it, now this is just a stepping stone pet.
4. Now find a zone with pets 1-2 levels above the pet you just catched.
5. Goto #3.
With this method (and if you don't get distracted and OCD by having to catch a rare or a cool pet) you will have a few lvl 23 pets quite quickly.
Skip doing any tamer quests until later. Those are excellent for boosting pets later on.
The "Arcane Eye" and "Restless shadeling" pets are giant stepping stones. Its 16-18 and always fights alone making it a very easy catch. You can skip 4-5 levels by going there and catching it with lvl 13-15 pets sacrificing them while taming it as there is no need to kill off additional pets.
*clarification*
The highest level you can get after a catch is lvl 23 (a lvl 25 downgraded). After that you can start boosting in Vale and levelling your disposable to lvl 25 at the same time.