So, a couple of months ago, I "adopted" a horse. Really, I just decided to groom, re-train, and play with her. She is a 17 year old mare who was used primarily for breeding for the past ten years. She has not been ridden in forever, and I'm pretty sure she was never fully broken. I have tried to ride her with a saddle, but her weak back can't support the heavy leather. I have been trying to find her a lighter saddle, but I can't really afford to buy one right now. So, I have been riding her bareback. She does a lot better, but she is still very stubborn. She won't stand for me to get on, she hops and mini-bucks when I urge her on, and sometimes she just flat-out refuses to move when I ask her to. I don't hit her. I squeeze with my legs and sometimes give her a kick. But I think the problem is a bit more deep than that.
So, how am I to go about re-training her on a very limited budget?