Hello! The equestrian forums are for real life horse topics, but since you also posted this in the gameplay topic I'm almost certain you are asking about the game.

As the others have replied, it is really anything and everything.

Cheap horses
Superb horses
Superb horses that are hopefully cheap
Superb horses that are not cheap but worth their price
Horses with any kind of BM items
Foundations
Divines
Specific breeds, age, gender, coats
Uni/ draft/ donkeys
For collection
For breeding
For resale
With Equus or Passes, that depends on the buyer too.

and the list goes on

Locking now as this forum is for real life horsey things and also, we arent allowed to give opinions in the forums as everyone has their own ideas of what's good or not.