Hey maps!
If your trainer isn't helping you find and fit a saddle (A..fire her! hehee...seriously. That's a huge red flag in my professional book) then you can always consult the owner of your local tack shop. Explain to her your budget (at $500 you'll be looking at the used saddles but you can for sure find a great used one for that or less), and then see if she does fittings or can recommend someone in your area who does.
Remember...fit the horse first, rider second.
The Beval saddles are FANTASTIC and if the one you mentioned fits your horse and DD, then snap that baby up!
The stateline Tack saddles (the Kincaids) are garbage. I know. There's one gathering dust in my tack room because it fits no horse and no rider, and puts the rider in a very chair seat position. Blech.
One of my students was test riding a horse she was considering and the horse had on a Circuit Elite saddle (the brand name that DOver Saddlery has), and she loved it. Said it was very much like the $3k Butet one of my other students rides in. Brand new they are $700ish.
I enevitably get a few parents each holiday season in your position, asking me what saddle to get their kid for Christmas. I always say, buy them a gift certificate to the tack shop or to Dover Saddlery for the amount you want to spend on a saddle...then take the kid shopping after the holiday to find one that fits.