So you want to go backpacking. Or car camping. Or hiking. But you're on a budget, and that can mean you're restricted to when it's not cold, rainy, hot, etc. etc. or it might mean that you can't go out for more than a few hours due to not having a tent or the appropriate gear.
I won't argue that high quality outdoors gear is expensive. But! There are ways around it. As you work to build up your collection of great gear, there are a few places you should always be checking for when that sweet piece of equipment you've been looking for shows up.
REI: They have seriously good sales, and while everything they sell might not actually be great, you can find some pretty good stuff. Also, make sure to go EARLY during their Garage Sales! You can find so much great gear for a really great price, just make sure to do your research before hand so you're not getting something shitty.
Goodwill: Laugh if you want to, but if you go to a well situated Goodwill (i.e. near expensive colleges where there are students that hike, near mountain regions, etc.) your Goodwill might be full of awesome gear that you can get cheap. Head in and look for name brands that you know, trust and love.
Walmart: You can get some good pieces here, especially the kind of stuff that just naturally often needs replaced. Like sock liners (get the white dress socks! they work!) batteries, flashlights and other things. The quality isn't guaranteed to last forever, but if its an item you'll have to replace a lot anyways, it's not worth spending a lot on it to begin with.
Military Surplus: You can find some great basics here (like long johns) but don't get any of their really heavy stuff.
Second hand outdoor good stores: Not all areas are lucky enough to have these, but some areas that have a lot of people buying and then never using their outdoors gear have really awesome second hand stores. Prices won't be as cheap as Goodwill, but you're more likely to find what you're looking for! Do some research and you might find them.