What the heck riding helmet are you looking at that's $350? I got a very nice one for 40.
You have to pick and choose what you need. Do you NEED riding jeans? The price is the reason I don't have any. Things can be reasonable, you just have to hunt for them. Horse.com and Chick's saddlery often have very good prices for pretty good products. :)
Just a start anyway. Also you don't need the equestrian jeans. They are made for being in the saddle all day every day. Unless you are on a working ranch or training horses you will be fine. I ride in my Levi's all the time and they last me even when I was riding 3 - 5 horses a day 6 days a week.
While in some cases, you "get what you pay for" in terms of quality and comfort, many (if not most) products marketed to equestrians are quite marked up. In terms of clothing, there are many places where you can find a pair of decent breeches for under $50. You'll save even more money if you buy second-hand, and there are many online resources where you're likely to find someone who is selling what you're looking for.
Some things you will want to invest the money in. When it comes to safety and/or comfort (ie. For tack and helmets), you really want to ensure that you buy something that is well-made, funtional, and suits your needs. However, that doesn't mean you need to go spend $350 on a Charles Owen helmet if you're just beginning lessons. However, do expect to pay somewhere in the $100-$150 range for a decent, well-fitting helmet (unless of course, you're one of the lucky people who fit an even less expensive helmet!)
I ride in Thrift Store jeans that run from $2-10. No stains, no holes, just outgrown by someone and passed on.
My helmet is Troxel, and cost me $48 including an upgrade to it's basic version and a design on the cover.
My boods are RedHead and cost me $40. I walk, ride, slosh through mud, muck, and run in them.
My shirts are just old t-shirts, not wrinkled or holey but likely to have a bit of horse snot on them.
And you know what? My horse don't know the difference at all ;) she rides the same whether I'm in my Sunday bests or trash clothes that I use for chucking bales of hay. You can avoid becoming poor by realizing that riding is more than the brand on your underwear tag ;)
You get what you pay for where a lot of things are concerned. Saddles, bridles, most leather products, etc. and some riding gear. Not in the sense that your regular, lower priced riding stuff is bad, but in the sense that some of the expensive expensive stuff can turn 'poor tastes' into 'rich tastes' easily
Oh just to add... though I am sure it goes without saying. Never buy a helmet used. Its one of those things you just don't skimp on. And avoid the Troxel helmets as the harness on them is known to become loose during your ride. I am a huge fan of Ovation helmets. I have one of the "upgraded" versions so I can use it showing. I only paid $120 for it and it looks great. Its light as a feather and well ventilated for riding in the heat and the liner can be removed to wash it when it gets stinky and sweaty lol.
Ideally I would have the GPA Speed Air but I haven't robbed a bank recently and have more important places to spend the money haha.