If you are looking for something cheap but has potential, you should try your local market, ino its not really a nice place but ive been a couple of times and you would be suprised sometimes x
am not sure what they are like to ride in or anything but i enquired about one to my saddler and she sed she wouldnt go near one, she said something the saddle depends on the tree, therefore it just doesnt work! dont quote me on that but ino she definatly doesnt like them, and shes a master-saddler!
just think of it as if theres blue smarties and red smarties in your horses stumach, and you want to swap the blue with green, so you chuck a load of green smarties in and the blue ones get angry and upset the horses stumach, where as if you just add a little green smarties then gradually build...