Yeah, it's a big mistake to think it's essential to buy expensive gear to have fun in the backcountry. As far as buying things cheaply, I've gotten a lot of gear through thrift stores, as well as REI sales and the North Face Outlet. My old REI backpacking backpack I got for $7 in new shape at Goodwill: not a high end pack, but boy did I have some fantastic trips with it before it fell apart! And I just bought another identical pack for $10 at a yard sale, also practically new, which I will mostly use mostly just when I fly and don't want to tear up my good pack, or when I want to lend it to someone visiting. I regularly use an Addidas down vest I bought for $4 at Goodwill years ago. My buddy, who likes to spend money more than I do, was trying to get me to buy a Marmot down vest on sale the other day. Well, sale or no sale, It's still was $60, and my present one works just fine in its role as a vest/pillow. Could I save a few ounces? Sure, but it doesn't. seem worthwhile to spend $60.
Anyhow, new top notch gear is very nice (I love my Big Agnes tent!), and now days I can afford to spend more than I use to, but I have also had some extraordinarily wonderful times using cheapo gear, too..