Actually in the theory, you can get all kind of pets between level 1 to 15 for Goddess Training. (Allthough I kinda find that lv 10-15 is too old.)

There are 3 rules for a good pet:
- speed
Fires must have lower speed than the pets and all pets can better have about same speed. (in range of 10)

- power
Maybe it is a little, but it helps very well to have more exp. How more damage, how more exp.

- advantage
Fire beats wind, wind beats earth, earth beats water, water beats fire. If fires are only who can attack, then the wind mob will give you the most exp, right?

In short, you need a pet that is fire and have a great speed and good power. For so far the red horse is the best pet for goddess training.

But you can use your express pet in the training and when it is level 10, just disband him and catch a new express pet. Very easy for superlow members, but why would they do that. They haven't good skills yet and their skills are still not maxed. So they need to train more until they have good skills and also maxed! Besides higher level players have often good things which they can lower their speed. Especially fire players. Too bad there are still noobs who lied about their speed, but it is really unneed, because they won't get good exp, if they lied about their speed.

So it was my conclusion. Just follow the guide: http://wlodb.com/topics/169
Then it will be fine.