I was in your same boat last fall. My budget was around 500-700 so I bought what I thought would fit us - a used Klimke Miller. Well, it didn't fit either one of us and my trainer said to get rid of it. I purchased a wintec thinking this will get us through but I hated it. I ended up selling that on eBay for the same price as I paid (whew!). My saddle search continued - you name it, I probably tried it. Stubben, Passier, Bates, Barnsby, Niedersuss... the list goes on - they were all used. Either it would fit me or my horse but only one fit the two of us... my trainers custom Schleese. I know, I know... you can't afford a custom, well neither could I and even if I could, I wouldn't be able to convince my non horsey hubbie to allow me to spend the $$. So, I ended up selling that used Klimke on eBay and a bunch of other tack that I wasn't using... I cleaned out my closets and while I was doing this, found pretty much the exact same Schleese that sat in someone's house with hardly little use for a price that was "just outside" of my budget. In selling the saddle, old clothes, old tack, I had $1300 to spend and paid $1K for my schleese (the lady spent $3500 on it) and had spare change! My point is, it took me several tries on used saddles and I do have a difficult horse to fit (x-tremely high wither and a flat back) and I knew what I bought initially (if it wasn't adjustable) I would have to get rid of later. I had time on my hand and an all purpose Stubben to ride in and even my trainer let me borrow her Schleese. If you have time and a way to generate a few xtra bucks you can find what will work but it has to work for both you and your horse or else your budget will be wasted on an ill-fitting saddle. Good Luck.
"The Horse: Friendship without envy, beauty without vanity, nobility without conceit, a willing partner, yet no slave."