If you are thinking about hammock camping, take a look at Shug Emery's Youtube channel. If you are planning to camp on the ground, you need to consider your whole shelter system, your sleeping pad, bag or quilt, bivy or ground sheet, if any, and tarp or tent. All of these things work together to keep you dry and comfortable. In the Midwest, I would not sleep on the ground without a groundsheet or bivy, just too much moisture in the ground. Where I live, it is very exposed and the rain falls horizontally because the wind only stops when it's hot. A bivy without a tarp is probably not a good idea. My own ground system is a MYOG bivy with a thin polyethylene foam half pad, a small self inflating pad, a MYOG Climashield quilt and a MYOG tarp. In cold weather, I'll revert to my old down bag. If you sleep cold, down is your best option. I have bought some down bags on eBay for $50 or so. You can often get some decent ones that people don't want anymore. You need to know what you are buying before you commit yourself, but some of the old bags are quite serviceable. The biggest problem with the old bags is weight and lack of compressibility. Synthetic bags are also hard to compress and don't usually have as much loft as premium quality down. Another eBay possibility is a beater down jacket (also part of your sleep system). Housewrap is another low dollar option. This can be used for groundsheets and tarps if you can find some scraps at a construction site. It's noisy and a bit heavy, but can also be used to mock up some ideas. If you have a backyard to try your stuff in, use it. I do. I don't want to get out to the middle of nowhere to find out that my brilliant idea doesn't work. It's also a good way to figure out refinements to your system before you go.