since its summer, you dont need a real nice sleeping bag. I use a $10 50 degree coleman fleece bag from big lots (i wouldn't suggest it in the other 3 seasons though, lol). as a cheap and lightweight alternative to a tent a just sleep in a hammock. 100 feet of rope, a nylon hammock, a 10x12 tarp, some tent stakes, and maybe a bug net. sounds like alot, but alot more compact than a tent and a therm-a-rest. its also really comfortable but takes a night or two to get used to. i've slept through a pretty bad storm with this set up and didn't get a rain drop on me. but whatever you do just check out www.sierratradingpost.com
and don't forget a water filter. msr miniworks for $70 is what i suggest; more expensive than iodine tablets but much better tasting. i bring packets of crystal light powder ($4 at publix) with me so i don't get tired of water.
heres a picture of my hammock set up. i have 2 25 foot sections of rope tied with a bunch of loops in them so i can set my hammock up in about 2 minutes; just wrap the rope around two trees and clip the hammock to the appropiate loops.