I have recently ridden in a friend's brand new Dover Circuit Saddle. It was squeaky, impossible to change the stirrup length (I had to ride in longer stirrups because they wouldn't budge) and a little dangerous because the girth was tight when I walked out of the stall, and loose by the time I was mounting up. Good thing my instructor noticed or that would've ended badly. I am a weakling, but I was so surprised how much the new leather was hard to stretch or adjust. Now these saddles are decent but I hated the feeling of riding in a new stiff saddle.
I just bought a used Stubben on Ebay
. It has the softest leather, only god knows how old it is but it is in beautiful condition, and I can adjust the stirrups and such as I please. I haven't had the chance to ride in it yet, but just feeling it and seeing it, I would never buy new again. It's such a pain to break in a saddle, and for your first horse, you're not sure what you or the horse may want. If I were you, I would buy a nicer, used, well-made and well-known brand. You can find great deals on them all over the place, an as you and your horse change, you will be able to afford different saddles as you learn what you like and you don't like. Just because a saddle works now doesn't mean it will work after you've owned the horse for a year and have kept it/worked it differently.
Basisally, used tack is worth it as long as you know your stuff and know what brands/condition to look for. Good Luck :)