A hammock and tarp are perfect for shelter in the summertime. I have a Eagle's Nest hammock and a silnylon tarp (those aren't cheap, least not the good ones) in case it rains. Mine is catenary-cut, so it is sort of like two trapezoids sewn together on the longest sides (well, that is the best way I can explain it anyway).
The hammock compresses down to the size of a grapefruit, and it is strong enough to hold 400 lbs. To me it is more comfortable than sleeping on the ground, but in the winter I have to go to great lengths to keep warm in it so I use the tent.
If you get a tent, make it easy on yourself and get a freestanding one. That way the tent can be setup without having to stake it down first.
If you decide you are on top of a rock or just don't like that guy in the tent next to you that snores, simply unstake the tent and move it, then re-stake it. A non-freestanding would require you to take the tent down, move it, then set it back up.
When you get ready to take down the tent, unstake it hold over head with the door unzipped, and shake out the dirt and leaves before you pack it.
Good online sites for cheap gear:
eBay - New & used electronics, cars, apparel, collectibles, sporting goods & more at low prices
(yes, some of my best finds were here)
Sierra Trading Post - Save 35-70% on Famous Name Brands
REI: Outdoor Gear & Clothing for Skiing, Snowboarding, Snowshoeing, Camping and More
(watch for clearance deals, they have an outlet site off the main page too for really discounted stuff)
Outdoor Gear from Campmor - Clothing, Camping Equipment and More - Top Brands including North Face & Columbia Sportswear
Remember that you typically get what you pay for, but there are some cheap gems out there that are as good as the best stuff.
That Teton is a great backpacking and touring tent. The Teton 2
For $100 it is well worth it, and gets lots of use in my collection of tents (I have three). Those huge, obnoxious Wal-Mart dome tents are good for 'car camping' with the family, but too heavy and bulky for touring IMO.
You can get cheap closed cell foam pads at Wal-Mart, and they work fine but do not compact down as much as the inflatable (Thermarest) ones.
Headlamps are a dime a dozen at Wal-Mart - the one difference between most of those and the more expensive ones are that the cheap ones generally lack a regulated circuit so they consume more batteries. If you can readily get batteries that is not a concern, but if you are hiking at dark and are 50 miles from the nearest town you want one that is regulated to conserve power.
Coleman makes a cheap pack stove that works great for cooking for one or two people. Amazon.com: Coleman Exponent F1 Ultralight Backpacker Camp Stove: Sports & Outdoors
Cheap army surplus stores - they have good stuff generally but it may be heavy (canvas backpack anyone?
Thrift stores and yard sales may have some hidden gems too. If the item is name brand and well cared for chances are it is going to hold up, and you'd pay pennies on the dollar for one.
I dare say that you could comfortably outfit yourself with *everything* you need to camp for $300 or less. Then you have the gear for touring, hiking, or just camping. The bulk of that cost would be sleeping bag and tent, and I would not suggest you skimp on either.
Teton2 - $100
Kelty Teton 2 Tent from Campmor
Kelty Cosmic 20deg synthetic bag (long) - $70.00
Kelty Cosmic 20° Thermolite Quallo Sleeping Bag Long from Campmor
Thermarest self inflating pad - $40.00
Therm-A-Rest Trail Medium Sleeping Pad from Campmor
Princeton Tec Aurora led headlamp - $16.00
Princeton Tec Aurora Headlamp from Campmor
Brunton Raptor butane stove $40
Brunton Raptor™ Foldable Butane Canister Stove from Campmor
MSR Blacklite cookset $44
MSR BlackLite™ Cookset from Campmor
Fuel cannister - $5
Folding utensils - $15
Alpine Folding Utensils from Campmor
Well, that was just my first shot but all that for $330, and all of it is decent name brand stuff. You could easily buy a backpack and set out with that gear, although eventually you 'd want the more expensive, lighter-weight stuff.