You need to match the top skills of the horse to the competitions then choose the closest match. You can change the speciality up to the age of 5 which gives you a chance to make sure its right. With correct training any breed can do well in any competition.

The Breeders Manual section 3.3 tells you the skills needed for each comp.

The Howrse-Breeding forum will help with schedules for any breed depending on its skill set.

As a general rule breeds with speed as one of their top skills do best in Classic. Breeds with stamina as one of the top skills can excel in Western although there are exceptions to this.

Thank you! I really appreciate it!